CYYJ
Michael
Hello All:
This past winter, I wanted to overhaul the front forks on my 2012 ST 1300. When I began looking for information about how to do this, I knew nothing about the front forks, they were a complete mystery to me.
I started doing research here in our forum and discovered that we have a huge treasure trove of wisdom & advice about front fork maintenance, but that information is all over the place. This article provides an illustrated guide to front fork overhaul, with inline citations linking back to all the various posts that others have made that I found so useful. I haven’t added any new information at all… all the knowledge here has been contributed by others. Special thanks and 99% of the credit for this article goes to Dave D., Larry (Igofar), and Jim C-G. All the valuable nuggets of information came from them - any errors and omissions are my fault, not theirs.
After having done this work for the first time myself, I came to the conclusion that the overall level of difficulty is low, but that the task is complex and there are ample opportunities to screw things up if you do not follow the Service Manual instructions carefully, and if you are careless in how you handle the disassembled parts.
Planning the Project
Overhauling the front forks – by that I mean taking them completely apart for inspection, rather than just changing the oil – is an ‘off-season’ task. Once you have the forks apart, you might discover that you need to order some parts. Also, once you have the front wheel removed and the forks removed, you might choose to do some other maintenance in that area such as front brake pad replacement, wheel bearing inspection and replacement, or cleaning the radiator. Because of the likelihood of “project creep”, I think it is best to do the front fork overhaul during a time of year when you don’t plan to ride the moto.
Tools Needed
Not very many tools are needed. I was able to get everything done with the following tools:
Consumables Needed
If, like me, you have no idea at all how forks work and have never serviced a fork before, you will want to do a fair amount of reading and video-watching before you begin. There is a lot of great information out there, here is where to find it:
Delboy’s Garage, “How To Replace regular type fork seals”: This video doesn’t go into full detail about how to overhaul and service forks, but it does provide an excellent overview of how to disassemble and work with a fork. By coincidence, he uses a fork from a ST 1100 in this video. The ST 1100 fork is similar, but not identical, to the ST 1300 fork. The biggest benefit of this video is the wealth of information about general workshop practices when servicing forks.
Fellow forum member Jim C-G’s video “Replacing Front Fork Seals & Springs on a ST1300”: This is an excellent video, it takes you through the complete process of disassembling ST 1300 forks, shows the forks fully disassembled, and generally takes all the mystery and fear out of the process.
Delboy’s Garage, “How To Re-Align Motorcycle Forks the Easy Way” : This video doesn’t address fork overhaul, instead, it provides interesting advice about how to go about the final stage of re-assembling everything to ensure that the geometry of the handlebars, front forks, and front wheel is set up correctly. Watch it before you begin work, then refer to it again once you have finished the overhaul of the forks, but before you install the front fender and begin to tighten everything up.
“ST1300 front fork oil replacement” here in our forum: There is some really useful advice in this thread, in particular Dave D’s (Dduelin) posts.
“Fork Seal Replacement and Sonic Spring Installation” here in our forum: Some models of handlebar risers interfere with access to the 17 mm hex caps on the top of the forks. This article illustrates how to work around this problem without having to remove the handlebars and riser. This article goes on to discuss changing to a different spring, and manufacturing and installing a different length spring collar – just ignore all that complicated stuff if this is the first time you have taken a fork apart and all you want to do is overhaul it and keep it in OEM configuration.
“Front Shocks Removal” here in our forum: This is another post where there is discussion about modifying (rather than just servicing) the front fork assembly, but there is a heck of a lot of good information about servicing the forks in that 4 page long thread. Well worth a read, just ignore anything that addresses modifying parts and don’t get too preoccupied with the discussion of “sag”.
“Fork Oil Questions” here in our forum: There is some useful information in this discussion to assist you in choosing what specification of oil to put in the forks.
“Help with fork disassembly” here in our forum: Some owners have encountered difficulty removing the small bolts from the very bottom end of the fork. I didn’t have any problem at all removing these bolts, but, it’s helpful to know that advice is available if a problem arises.
“Fork Vertical Alignment” Contains an excellent suggestion about how to ensure that the two forks are perfectly aligned when you reinstall them. A tiny offset error in vertical alignment probably won’t affect ride quality, but it will make life difficult in the future when you remove and replace the front tire.
“Motorcycle Fork Stiction” This video suggests that you stuff some rubber-compatible grease into the top of the fork slider, on top of the fork seal, before you install the dust cover. The Honda maintenance manual does not mention this. I’m not sure how important this idea is but stuffing a little rubber-compatible grease in there certainly will certainly reduce the risk of corrosion of the inner landing surface of the fork slider and corrosion of the stopper ring that holds the fork seal in place. It’s your own call whether to put grease in there or not.
Disassembly
Put the motorcycle on the center stand, then, remove the two black rubber caps that friction-fit into the middle of the caps at the very top of each fork tube. Fully loosen the single 12 mm pinch bolt that pinches the very top of the fork tube on each of the forks. Using the 17 mm hex tool, crack open the cap on the top of each fork. Don’t remove it at this time, just loosen it half a turn (it needs about 8 turns to be removed).
Using a jack under the front of the engine, jack the bike up until the front wheel is an inch or two off the ground. Put the wood blocks under the engine and then lower and remove the jack so that the front wheel is still off the ground, supported by the wood blocks under the front of the engine.
Remove the front fender and set it aside. Remove the two bolts that hold each brake caliper in place. Remove all four pinch bolts from the bottom of the forks. Remove the axle from the front wheel, then remove the front wheel and set it aside. You might want to inspect the front wheel bearings and clean and lubricate the dust seals on either side of the front wheel at this time.
Other than the front fender, I did not have to remove any Tupperware from the motorcycle during this project.
The piping that delivers fluid to the front brakes is attached to the forks with two bolts on the right fork and one on the left fork. Remove these three bolts. You will need a thin 10 mm open-end spanner to loosen the upper of the two bolts on the right fork – you can’t get a socket in there because the swaged hose fitting blocks access.
Before you go any further with the disassembly (but after you have disconnected the brake piping from the top of the two fork sliders), crack the two socket bolts (hex bolts) in the very bottom of the fork slider loose. You can do this by holding onto the fork slider with your hand and then stuffing a hex key into the bottom of the fork. I was able to crack both bolts loose with a quick snap of my wrist. If you have difficulty, you can partially insert the flared end front axle into the side of the fork down at the bottom and use it to hold the fork leg still when you break the socket bolt loose. Don’t unscrew the bolt any more than necessary to break it loose, otherwise, fluid will leak out.
Larry (Igofar) gave me some very wise advice before I began: “Only remove one fork at a time – never have both forks removed at the same time”. This is important. If you always have one fork installed, you won’t encounter problems later trying to get the front fork lock to engage when you remove the key from the motorcycle. Also, the shiny fork tube is susceptible to damage… if you only have one fork removed at any given time, this lessens the risk of damage to the other one.
Its most efficient if you remove the right-hand side fork first, because this will save a few extra steps when it is time to re-assemble and vertically align the two forks.
Dave D (Dduelin) also gave me some excellent advice. He wrote: “When clean and in the proper lighting at 72,000 miles, I could see a slight 'haze' on the leading side of the fork tube where airborne sand or debris had dulled the chrome. After that discovery, at each fork service I mark or index the fork tube with a piece of tape and a magic marker and rotate it 90 or 180 degrees upon reassembly and even up this minute wear.”
Now, fully loosen the two 12 mm pinch bolts on the right-hand side lower fork clamp. I suggest you loosen the upper one bolt first. Hold onto the shiny fork tube when you loosen the second of the two bolts, to prevent the whole fork assembly from suddenly dropping down.
The chrome surface on the shiny fork tube is fragile. It can withstand most insect impacts, but it can’t withstand banging against another metal surface (like the fork clamps, or your toolbox, etc.). If you nick, scratch, or otherwise damage the chrome surface, your only option is to buy a new fork tube, and that costs about USD $190.00 plus shipping (P/N 51410-MGS-G02).
Disassembling & Draining the Fork
Once you have the fork off the motorcycle, you start disassembly at the top.
Grab the shiny fork tube with your hand and use the 17 mm hex key to unscrew the fork cap from the top of the fork (now you know why you broke it loose before you removed the fork from the motorcycle). It will take about 8 full turns before the fork cap comes off. My experience was that the fork cap only popped up a little bit when it finally disconnected, so I don’t think it is a big safety hazard, but don’t have it pointing at your face when you unscrew it. Refer to the 5:00 minute mark in Jim C-G’s video “Replacing Front Fork Seals & Springs on a ST1300” to see how much movement to expect when the fork cap comes loose.
Once the fork cap has been unscrewed from the fork tube, you need to remove the fork cap from the top of the form damper rod. To get access to the nut below the fork cap, shove a 12 mm open end spanner UNDER the nut, and push down on the end of the spanner to displace the spring collar (the steel tube). Then, put a 14 mm spanner on the nut, hold both spanners in one hand, and unscrew the fork cap with your other hand.
Set the fork cap and the spring collar off to one side and invert the fork over a drain pan to drain it out. Not much liquid will come out – perhaps a little more than half a liter (one pint).
The spring will fall out when you invert the tube, so tip the tube slowly and be prepared for the spring to come sliding out. The ‘spring seat’, which looks like a very large washer, will also fall out into the drain pan – don’t forget to fish it out and set it aside.
While the fork tube is inverted and draining into the pan, you can remove the small socket bolt and its associated copper washer from the bottom of the fork slider. Once the bolt is removed, the whole fork damper assembly will slide downwards into the drain pan.
By now, all the oil that is going to drain out of the fork tube will have drained out, so lay the fork tube / fork slider assembly down on a piece of carpet (so as not to scratch the fork tube) and pull the fork damper out. It will have a silver colour cap on the end (by my fingers in the photo below), remove this cap and set it aside. No further disassembly of the fork damper is possible.
Put the bottom end of the fork damper in the drain pan and pump the rod of the fork damper up and down. It will take a couple of dozen full cycles to get most of the oil out of the inside of the damper. Once oil stops coming out of the damper, turn the whole damper assembly upside down and continue to pump the rod through its full length of travel. Some additional oil will drain out.
Once you have drained the damper as best you can, leave it upside down (thin tube down) to drain in the pan, and pick up the fork slider and tube assembly. Remove the dust seal very carefully, using a dull butter knife.
Dave D. (Dduelin) suggests the following technique: “I learned to use a butter knife to pry the dust seals out. It's less likely to scratch the leg or tube and it's quick. Insert the knife like you were preparing to cut the tube in half and when the blade edge is against the tube I kind of just lift the handle end to twist the blade as a lever and pop the dust wiper out. A small flat blade screwdriver doesn't move the seal much when twisted and the butter knife is dull. The butter knife can also be used to pop the stopper ring out.”
There is a great risk of scratching the chrome surface of the fork tube when you do this, so go slowly and don’t apply too much pressure inwards toward the tube – apply your pressure upwards. You will need to work your way around the dust seal several times to get it loose.
Once the dust seal is removed, you need to remove the stopper ring (a big circlip) that holds the fork seal in place. Once again, be very careful to not accidentally scratch the fork tube with the very sharp ends of the stopper ring. Use the butter knife to get one end of the ring loose, then keep a finger over the loose sharp end as you work around the rest of the ring, prying it loose from the groove that it fits in.
After removing the stopper ring, you can separate the fork tube and its attached components from the fork slider by just pulling the two pieces apart. See the 5:50 minute mark of Jim C-G’s video “Replacing Front Fork Seals & Springs on a ST1300” to see how this is done.
After the fork tube comes out of the fork slider, you can remove the oil seal, the backup ring (looks like a huge washer, bigger than the spring seat), and the smaller of the two bushes by sliding all three parts up and over the top of the fork tube.
Honda’s nomenclature for the two bushes is inconsistent. In the Service Manual, the smaller of the two bushes – the one that fits into the top of the fork slider, just below the oil seal – is labelled ‘slider bush’, and the larger one that clips around the very bottom of the fork tube is labelled ‘fork tube bushing’. In the parts catalog, the smaller one is called ‘bush, guide’ and the larger one is called ‘bush, slider’.
You can then remove the fork tube bushing (the large one clipped around the bottom of the fork tube) by prying it open a wee bit with the small screwdriver and then sliding it over the bottom end of the fork tube. Don’t pry it open any more than necessary, otherwise, you will deform it and you won’t be able to use it if it is otherwise in satisfactory condition.
At this point, you have fully disassembled everything, and the parts look like this if you lay them out on your workbench. Compare the photo below to the illustration on page 15-28 of the service manual.
Now, gather everything up and take the parts inside to your laundry sink. Wash them all using a soft cloth and lots of Simple Green or citrus degreaser. Except for the damper rod, cleaning all the parts is straightforward. Be careful when cleaning the inside surface of the fork slider (the female part of the fork assembly) – that surface must not be scratched, it is as critical as the outer surface of the fork tube. I wrapped a microfiber cloth around the end of a wooden broomstick to clean all the deposits off the bottom inside surface of the fork slider.
Consider using a soft Scotch-Brite pad or fine grade bronze wool (not steel wool) to clean up any corrosion present on the inside top area of the fork slider, where the oil seal, stopper ring, and dust seal fit. Bronze wool is available at most Home Depot stores and at ship chandlers. On my forks, it was evident that water had accumulated in there at some time in the past, which makes a good case for putting some rubber-compatible grease on top of the fork oil seal during reassembly, as suggested in the video “Motorcycle Fork Stiction”.
The damper rod assembly requires a lot of attention, because no matter how many times you pumped it when you had it over the drain pan, there will still be a heck of a lot of old oil and debris inside it. Fill a small cup with a solution of warm water and Simple Green or citrus degreaser, put the bottom end of the damper rod in the cup, and pump. You’ll need to change the solution several times before it remains clean. Pour or spray some undiluted Simple Green or citrus degreaser over the upper end of the rod and pump again – a lot more gunk will come out. Invert the damper rod so that the thin rod is at the bottom, pour or spray some undiluted Simple Green or citrus degreaser into the ‘base’ of the assembly (the part at the top), and keep pumping. It took me about 15 minutes of work to completely clean out the inside of the damper rod assembly.
Once you think you have it as clean as can possibly be, stand it up upside-down on top of a rag (with the narrow rod at the bottom) and leave it overnight. A whole lot more gunk will drain out of the narrow rod overnight. I kind of suspect that this is where the fine granular particles that wear off the sliding surfaces of the bushes accumulate.
Evaluating the Condition of the Bushes
The bushes have a brownish-grey Teflon-like coating on one side, and a copper colour coating on the other side. The condition of the copper colour side doesn’t matter at all, unless the surface is grossly deformed. The copper colour side is fixed, in the sense that it does not move, it stay put. So, if you see evidence of some wearing away of the copper colour, that alone is not a reason to replace the bush (but it does explain where all that debris in the damper rod came from!).
It’s the brownish-grey side of the two bushes that matters – this is the side that slides. On my motorcycle, which had 90,000 km (55,000 miles) on it when I did this work, the Teflon-like coating on both smaller bushes was in fine condition, but the coating on one of the larger bushes was worn away on one side only. Because I had already ordered two of each size of bush, I replaced all of them… but the Service Manual states, on page 15-26, that replacement is only necessary if the bush is scored or scratched, or if the Teflon-like coating is worn away on more than ¾ of the surface.
On the other hand, though, if you have gone to all the trouble of fully disassembling the forks, you might as well replace all 4 bushes. A set of 4 costs USD $25.00 net from Partzilla at the time I write this (that’s about $300.00 Canadian after currency conversion, duties, taxes, and shipping are added), so, for USD $25.00, you can be reasonably assured that you won’t have to fully disassemble the forks for another 100,000 km (60,000 miles) or so – all you will need to do until then is just drain & change fork oil, which is a much simpler & faster process.
Evaluating and Correcting the Condition of the Fork Tube
The fork tube is subject to impact damage from rocks and hard-shelled insects. If it has suffered impact damage, there’s not much you can do about the impact crater, but what you can do is make sure that there are no ridges around the crater that stick up and will damage your new fork seal.
I found a small impact crater on one of my fork tubes. I used a Norton ICE 2000 grit foam finishing disc to abrade away the raised edges of the crater, and followed up by polishing the outer surface of both fork tubes with Meguiar’s Mirror Glaze 9 Swirl Mark Remover. Both are specialty products available from auto body industry suppliers, they are not usually found at consumer retail stores. Fine grade bronze wool (not steel wool) could also be used.
There’s no point in perfecting the condition of the fork tubes, only to scratch them up when re-installing them, so take a moment to clean the inside of both the upper and lower fork clamps (still on the motorcycle) with a soft 3M Scotch-Brite pad, bronze wool, or similar gentle abrasive before you put the forks back on the motorcycle.
Putting it Back Together
Re-assembly of the fork and installation back on the motorcycle is quite straightforward and easy to do.
Lubricate the landings on the inside surface of the fork slider where the smaller bush, the backup ring, the oil seal, and the dust seal will go. I used rubber-compatible grease as the lubricant.
Lubricate the inside of the larger of the two bushes and install it on the bottom of the fork tube. Lubricate the outside of that bush, then install the fork tube into the fork slider.
Lubricate both sides of the smaller bush, lubricate the entire surface of the fork tube, then slide the smaller bush down the outside of the fork tube. Seat it in its groove using the genuine 85¢ Home Depot Honda ST 1300 fork bush seating tool. It’s easy to tell when it is properly seated by just looking into the top of the fork slider. Not much force is needed.
Install the backup ring. Don’t forget to install the backup ring. It is easy to forget to install the backup ring, don’t ask me how I know that.
Now, install the fork oil seal. Honda includes a little fortune-cookie like slip of paper telling you to install the fork oil seal with the manufacturer lettering facing up. To determine which side has the manufacturer lettering on it, just find the closest scanning electron microscope to your home and take the new fork seal there to examine it under the microscope. Failing that, the side of the oil seal that has the little square dimples embossed in it is the same side as the side with the manufacturer lettering.
In Delboy’s video “How To Replace regular type fork seals”, he suggests cutting up a plastic milk jug to use to protect the new seal when you slide it down the fork tube. An equally effective method is to use the plastic wrapper that the new fork seal came in to protect it as you slide it down the tube.
Use the Home Depot tool to seat the fork oil seal. Instead of ramming the tool down on the fork seal and risking deformation of the new seal, just press down hard on the tool and the seal will slip into place – assuming, of course, that you lubricated the inside of the fork slider where the seal seats.
The stopper ring (big circlip) will almost certainly be corroded. Clean it up with some bronze wool, then wash it thoroughly with soap and water to get rid of any bronze wool residue. Slide it down over the fork tube, put your finger over one end of the ring (to prevent it from scratching the fork tube), and poke the other end into the top of the fork slider using your other hand. Press the ring all the way down into place with the Home Depot tool. Visually confirm that the ring is fully seated through 330° in the groove within the fork slider.
If you choose to add some rubber-compatible grease on top of the seal and stopper ring, do it now, before installing the dust seal. Don’t add too much, because the dust seal almost completely fills the remaining space in the top of the fork slider.
Install the dust seal. Put a little bit of lubricant on the fork tube before you attempt to slide the dust seal down the tube.
Find the silver cap (‘oil lock piece’) that fits on the end of the fork damper and re-install it. If you put a wee bit of rubber-compatible grease around the base of the fork damper before you install the oil lock piece, it won’t fall off when you lower the assembly into the fork tube.
Lower the fork damper assembly into the fork tube. Apply a little bit of low-strength Honda blue threadlocker to the fork socket bolt (hex bolt) that goes in the bottom of the fork slider to hold the fork damper in place, then install the bolt and torque it to 20 N·m (14 foot-pounds). You might have to hold the nut at the very top of the fork damper to prevent the damper from rotating when you tighten the fork socket bolt… I didn’t have to, the bolt tightened nicely without any need to hold the fork damper rod.
Take it easy when applying the threadlocker to that bolt. Make sure you are using low-strength threadlocker. Later, when you put the axle in place, that bolt can’t escape, so all you are doing with the thread locker is ensuring that it doesn’t wiggle loose and let the fork oil escape. Chances are that you will be the person who next removes that bolt in another 60,000 miles… so, don’t make your future life difficult.
Adding the New Fork Oil
Stand the fork assembly upright. Lift the damper rod up so you don’t get it coated in oil when you add the oil.
Pour a little bit of oil – perhaps a few ounces (100 ml) – into the fork, and then firmly push the shiny chrome fork tube down to the very bottom of the cast aluminum fork slider. Then, pour more oil into the fork until the oil level is about 4 or 5 inches (10 cm) below the top of the fork tube. That’s less than the final fill amount, which will be added later.
Now, operate the fork damper rod through its full range of motion at least 20 or 30 times. Be sure to push it all the way down – you will encounter some resistance about an inch from the bottom, don’t confuse that initial resistance with being the bottom limit of travel. After you have operated the fork damper rod 20 or 30 times, the motion should be smooth all the way up and down. The resistance will be different between the upstroke and downstroke, that is normal.
Now operate the chrome fork tube several times through its full range of motion, again being sure to hit the bottom on the way down. Finally, operate the fork damper rod once again, to confirm smooth operation through its full range of motion. You want to be certain that there are no air bubbles remaining anywhere in the bottom of the fork slider or within the fork damper rod assembly.
Honda’s specification is that the fork oil level should be 62 mm (a tiny bit less than 2 ½ inches) from the top of the fork tube when the fork tube is fully compressed into the fork slider. This is measured without the fork spring or the spring collar (steel tube) in place. It doesn’t matter where the fork slider rod is when you carry out this measurement, it can be in any position.
So, get your syringe with the 62 mm tube attached to it ready on the bench next to you, then pour fork oil into the fully compressed tube until it is about 2 inches (50 mm) from the top, then use the syringe to suck out the excess. Once you have done this, verify the 62 mm from the top measurement a second time using a different method (e.g. a ruler, or a pencil with a tape mark around it at 62 mm).
Closing up the Fork
Before you begin closing up the fork, you need to get some tools and components in place close by on your workbench.
Find the fork cap and install the new O-ring on it. Lubricate both the threads and the O-ring with fork oil before installing the O-ring. Place that assembly within reach.
Get the fork spring, the spring seat (smaller of the two ‘big washers’), and the spring collar (steel tube) within reach on the workbench. Get the 17 mm hex key installed on a torque wrench set to 20 N·m (14 foot-pounds). Place the 12- and 14-mm open end wrenches within reach on the workbench.
Pull the damper rod up as high as it will go and hold it up until you are ready to install the spring and spring seat (the rod will slowly sink down if it is not held). Extend the fork tube upwards until it reaches the top of the fully-extended damper rod.
Pick up the spring and the spring seat and place the spring seat on the top of the spring. Tilt the whole fork assembly sideways to about a 45° angle (this to avoid splashing when the spring slides down into the fluid) and drop the spring and spring seat into the tube. The pointy end of the spring (the tightly wound end) goes downwards. The spring goes in first, with the spring seat on top of the loosely wound end (big end) of the spring. As soon as you have dropped the spring and spring seat in, grab the top of the damper rod before it sinks down out of sight.
Press the fork tube down a few inches into the fork slider. Lift the damper rod up as high as it will go. Hold the damper rod up by sticking a finger in between one of the coils of the spring. Now install the spring collar (steel tube) over top of the damper rod. Grab your 12 mm open end wrench and stick it UNDER the 14 mm nut on the damper rod. Pry up the rod a bit (in effect, you compress the spring a bit) and hook the mouth of the 12 mm wrench over the far side of the spring collar.
Pick up the fork cap and spin it onto the threads of the damper rod. When it comes time to tighten it up, pick up your 14 mm wrench and install it around the nut in such a way that you can hold both the 12- and 14 mm wrenches in one hand. Now grab the torque wrench with the 17 mm hex on it and tighten the fork cap against the nut until 20 N·m (14 foot-pounds) of resistance is achieved.
Dave D wrote: “If someone adds preload with longer spacers or extra washers, it may become difficult to press the fork cap down and turn it to engage the threads of the cap and tube. There have been folks posting they couldn't do it alone and/or had great difficulties here. I advise them to press down the threaded cap using a ratchet or breaker bar with the 17 mm hex, hold the cap still, and with the other hand turn the tube to engage threads instead of trying to turn the cap and holding the tube still. It's simple but it works.”
Grab the spring collar with your hand, compress it slightly, and remove the two open end wrenches. Don’t let the fork cap, with its very fine and soft aluminum threads, slam against the top of the hard steel fork tube. Gently release the pressure you have been holding on the spring collar, and spin the fork cap – by hand, not with the wrench – into the threads of the fork tube. Screw the cap on all the way until the O-ring disappears into the fork tube, but don’t attempt to tighten it up solidly – the final torque will be applied to the fork cap once it is installed on the motorcycle.
Re-installing the Fork
Check the upper and lower fork clamps on the motorcycle and confirm that they are clean inside and that the three bolts (one on the top clamp, two on the lower clamp) are loose. Put a 12 mm socket on the shortest ratchet handle you have, then take the (right-hand) fork and the wrench over to the motorcycle. Insert the fork up into the two clamps until it is “approximately equal” (eyeball equal is good enough at this stage) in vertical alignment to the other fork. Don’t worry about being exact. Gently & lightly snug up the two bolts on the lower clamp just enough to prevent the fork from sliding downwards onto the floor. Don’t over-tighten the bolts – all three of these fork clamp bolts are steel bolts that fit into a much softer aluminum casting. Don’t be concerned about correct torque at this time, the right fork installation is temporary at this stage of the process. Don’t tighten the upper fork clamp bolt, it needs to remain loose.
The Other Fork (the left-hand fork)
Repeat the whole process on the other fork. It took me about 3 hours to do the first fork, and about 45 minutes to do the second fork. Once you have seen the first fork fully disassembled, you know what to expect with the second fork and the process becomes very simple and straightforward.
Re-install the second fork (the left-hand fork)
The process for re-installing the left-hand fork is the same as the process for re-installing the right-hand fork, except that you want to be more meticulous about getting the vertical position of the second fork correct.
The Service Manual doesn’t give a specification for how much the fork tube should stick up above the upper fork clamp. I chose to set the top of the left-hand fork tube 1 mm above the top surface of the upper fork clamp, this to reduce the risk of water puddling at the junction of the fork cap and fork tube.
Once you have the left-hand fork installed at the correct vertical height (relative to the upper surface of the top fork clamp), gently snug up the two bolts on the left side lower fork clamp. Again, don’t worry about correct torque right now, and don’t overtighten them.
To ensure perfect vertical alignment of the two forks, see this suggestion: Fork Vertical Alignment.
Now, install the axle partway through the right-hand side fork, loosen the lower fork clamp bolt holding the right-hand fork in place, and vertically align the left and right forks, using the axle as the reference point for vertical alignment.
Check to make sure that the vertical alignment of the top of the fork tubes “makes sense” above the upper fork clamp. The two fork tubes should protrude an identical amount, within 1 mm tolerance. Then, snug up the two bolts on the lower fork clamp of each fork. Don’t worry about correct torque at this time, these bolts will be loosened later.
Final Tightening of the Fork Cap and Upper Fork Clamp Bolts
The next step is to apply correct and final torque to the fork cap and the upper fork clamp bolts.
Because all the various bolts (about a dozen of them) in the fork system and the front brake calipers are safety-critical and need to be torqued to specific values, I suggest you get a small bottle of ‘White-Out’ or some other paint-on correction fluid, and use that to mark a bolt once you have applied the correct final torque to each bolt. If you want to use a product that is specifically manufactured for torque inspection, you can get a small tube of Dykem Torque Seal or similar from a specialty shop.
Check to make sure that the single 12 mm pinch bolt on each side of the upper fork clamp is completely loose. Now use your torque wrench with the 17 mm hex installed to tighten the fork cap to achieve 23 N·m (17 foot-pounds) of resistance - the two lower fork clamp pinch bolts that you snugged up earlier will prevent the fork tube from rotating. It might be a good idea to put a towel or pad over the gas tank before you start, just in case you drop the wrench, or it slips out of the fork cap when you are torquing it.
Once you have the two fork caps correctly torqued, apply final torque to the pinch bolt on the upper fork clamp on each side. This is a 12 mm bolt and the specification is 26 N·m (20 foot-pounds).
Finally, mark the fork caps and the two upper pinch bolts with the Torque Seal paste or with correction fluid to indicate that you have applied final torque to these items.
Aligning the Front End (Steering and Forks) of the Motorcycle
Delboy produced an interesting video titled “How To Re-align Motorcycle Forks the Easy Way". In this video, he shows how the front end of the motorcycle can become misaligned, and how to correct it.
If you are interested in carrying out this alignment procedure, now is the time to do it, because the only fasteners that you have applied final torque to are the two upper fork mount pinch bolts. If you are not interested in following Delboy’s procedure, skip ahead to the next section “Not Interested in Delboy’s Alignment Suggestion? Want to do it By the Book?”
If you are not interested in following the alignment procedure suggested by Delboy, and want to reassemble the front end as Honda directs on pages 15-32 and 15-33 of the Service Manual, proceed as follows:
The last step in the re-assembly process is to re-install the front fender. It is held in place by six fasteners. Honda does not specify a torque for these fasteners, therefore, “standard” torque based on the fastener size (listed at the top of page 1-13 of the Service Manual) are used.
If you use an aftermarket fork brace, install it now, after everything is back together, but be very critical when observing the fit of the fork brace when you put it into place. If it does not fit around the top of the fork sliders “perfectly”, with no friction or movement of any kind of the forks when you put it in place, you might just want to leave the fork brace off your motorcycle for your next few thousand miles of riding, and see what you think of the handling. I say this because if the width between fork vertical centerlines of the aftermarket fork brace is off by as little as one-thousand of an inch, it will introduce stiction to the front fork system that you just painstakingly overhauled, which may cause uneven wear of the bushes within the fork.
Final Safety Check
As mentioned earlier, all the fasteners used on the front forks and front brake are safety-critical. In the aircraft maintenance industry, all safety-critical fasteners must be double-checked by a second qualified person before the aircraft is released to service following maintenance. An “almost just as good” way of verifying nothing has been missed is to leave the motorcycle overnight, then double-check it the next day. Here’s the checklist, from the top down:
I hope this post is useful to others in the future, and once again, I thank Larry, Dave, and Jim for the contributions they have made in the past, without which I would never have have had the knowledge and confidence needed to overhaul the forks on my motorcycle.
Michael
This past winter, I wanted to overhaul the front forks on my 2012 ST 1300. When I began looking for information about how to do this, I knew nothing about the front forks, they were a complete mystery to me.
I started doing research here in our forum and discovered that we have a huge treasure trove of wisdom & advice about front fork maintenance, but that information is all over the place. This article provides an illustrated guide to front fork overhaul, with inline citations linking back to all the various posts that others have made that I found so useful. I haven’t added any new information at all… all the knowledge here has been contributed by others. Special thanks and 99% of the credit for this article goes to Dave D., Larry (Igofar), and Jim C-G. All the valuable nuggets of information came from them - any errors and omissions are my fault, not theirs.
After having done this work for the first time myself, I came to the conclusion that the overall level of difficulty is low, but that the task is complex and there are ample opportunities to screw things up if you do not follow the Service Manual instructions carefully, and if you are careless in how you handle the disassembled parts.
Planning the Project
Overhauling the front forks – by that I mean taking them completely apart for inspection, rather than just changing the oil – is an ‘off-season’ task. Once you have the forks apart, you might discover that you need to order some parts. Also, once you have the front wheel removed and the forks removed, you might choose to do some other maintenance in that area such as front brake pad replacement, wheel bearing inspection and replacement, or cleaning the radiator. Because of the likelihood of “project creep”, I think it is best to do the front fork overhaul during a time of year when you don’t plan to ride the moto.
Tools Needed
Not very many tools are needed. I was able to get everything done with the following tools:
- A 17 mm hex tool that fit on my socket wrench (about $10)
- 10, 12, and 14 mm socket wrenches and open-end spanners
- A 22 mm wrench (socket or box) for the front axle bolt
- 5- & 6-mm hex tools (or Allen keys)
- A very small slotted screwdriver
- A torque wrench with a range of 12 to 26 N·m (9 to 20 foot-pounds), and another monster torque wrench that can be set to 78 N·m (58 foot-pounds) for the front axle.
- An 85¢ “Honda ST 1300 Special Fork Seal Driver Tool” purchased from your local Home Depot (a Nibco brand 1 ½ inch PVC and/or ABS DVW [Drain, Waste, & Vent] coupling… get one of each material (PVC and ABS) if you can, the PVC one is great for the slider bushing, the ABS one fits the fork seal perfectly)
- A 10 ml syringe (available at any drugstore, about $1.00) and 3 inches of tubing to fit on the end of it.
- A big laundry sink where you can wash up all the parts
- A bottle jack or similar, and some scrap wood blocks to hold up the front end of the bike.
- A Honda ST 1300 Service Manual (pages 15-20 to 15-33 inclusive)
Consumables Needed
- 2 quarts (2 liters) of fork oil – nominally 10 weight
- A little bit of red rubber grease or brake caliper grease
- 2 Replacement fork seal kits (each kit includes one seal and one rubber dust cover), Honda PN 51490-MCA-003
- Some low-strength threadlocker (e.g. Honda blue). NOT Loctite Red, which is high strength.
- Two tiny washers for the plug at the bottom of the fork, Honda PN 90544-283-000
- Two O-rings for the cap at the top of the fork, Honda PN 91356-MW0-003
- Lots (at least a quart) of Simple Green or Citrus degreaser for cleaning up the parts.
- Some solvent such as Varsol or Stoddard Solvent for detailed clean-up.
- Depending on the condition that certain parts are in once you get everything disassembled, you might also need to purchase the following… but, I don’t recommend you buy these parts ahead of time, they only need to be replaced “on condition”. But, if only one side is worn (e.g. one guide bush is worn, but the other guide bush is OK), replace both guide bushes, this to ensure uniform friction on both forks.
- Two Guide Bushes, Honda PN 51414-MCH-003
- Two Slider Bushes, Honda PN 51415-MCS-G01
- 8 mm Socket Bolt for the bottom of the fork leg, Honda PN 90117-MCS-G01 (you will only need to replace this if you wreck it when removing it).
If, like me, you have no idea at all how forks work and have never serviced a fork before, you will want to do a fair amount of reading and video-watching before you begin. There is a lot of great information out there, here is where to find it:
Delboy’s Garage, “How To Replace regular type fork seals”: This video doesn’t go into full detail about how to overhaul and service forks, but it does provide an excellent overview of how to disassemble and work with a fork. By coincidence, he uses a fork from a ST 1100 in this video. The ST 1100 fork is similar, but not identical, to the ST 1300 fork. The biggest benefit of this video is the wealth of information about general workshop practices when servicing forks.
Fellow forum member Jim C-G’s video “Replacing Front Fork Seals & Springs on a ST1300”: This is an excellent video, it takes you through the complete process of disassembling ST 1300 forks, shows the forks fully disassembled, and generally takes all the mystery and fear out of the process.
Delboy’s Garage, “How To Re-Align Motorcycle Forks the Easy Way” : This video doesn’t address fork overhaul, instead, it provides interesting advice about how to go about the final stage of re-assembling everything to ensure that the geometry of the handlebars, front forks, and front wheel is set up correctly. Watch it before you begin work, then refer to it again once you have finished the overhaul of the forks, but before you install the front fender and begin to tighten everything up.
“ST1300 front fork oil replacement” here in our forum: There is some really useful advice in this thread, in particular Dave D’s (Dduelin) posts.
“Fork Seal Replacement and Sonic Spring Installation” here in our forum: Some models of handlebar risers interfere with access to the 17 mm hex caps on the top of the forks. This article illustrates how to work around this problem without having to remove the handlebars and riser. This article goes on to discuss changing to a different spring, and manufacturing and installing a different length spring collar – just ignore all that complicated stuff if this is the first time you have taken a fork apart and all you want to do is overhaul it and keep it in OEM configuration.
“Front Shocks Removal” here in our forum: This is another post where there is discussion about modifying (rather than just servicing) the front fork assembly, but there is a heck of a lot of good information about servicing the forks in that 4 page long thread. Well worth a read, just ignore anything that addresses modifying parts and don’t get too preoccupied with the discussion of “sag”.
“Fork Oil Questions” here in our forum: There is some useful information in this discussion to assist you in choosing what specification of oil to put in the forks.
“Help with fork disassembly” here in our forum: Some owners have encountered difficulty removing the small bolts from the very bottom end of the fork. I didn’t have any problem at all removing these bolts, but, it’s helpful to know that advice is available if a problem arises.
“Fork Vertical Alignment” Contains an excellent suggestion about how to ensure that the two forks are perfectly aligned when you reinstall them. A tiny offset error in vertical alignment probably won’t affect ride quality, but it will make life difficult in the future when you remove and replace the front tire.
“Motorcycle Fork Stiction” This video suggests that you stuff some rubber-compatible grease into the top of the fork slider, on top of the fork seal, before you install the dust cover. The Honda maintenance manual does not mention this. I’m not sure how important this idea is but stuffing a little rubber-compatible grease in there certainly will certainly reduce the risk of corrosion of the inner landing surface of the fork slider and corrosion of the stopper ring that holds the fork seal in place. It’s your own call whether to put grease in there or not.
Disassembly
Put the motorcycle on the center stand, then, remove the two black rubber caps that friction-fit into the middle of the caps at the very top of each fork tube. Fully loosen the single 12 mm pinch bolt that pinches the very top of the fork tube on each of the forks. Using the 17 mm hex tool, crack open the cap on the top of each fork. Don’t remove it at this time, just loosen it half a turn (it needs about 8 turns to be removed).
Using a jack under the front of the engine, jack the bike up until the front wheel is an inch or two off the ground. Put the wood blocks under the engine and then lower and remove the jack so that the front wheel is still off the ground, supported by the wood blocks under the front of the engine.
Remove the front fender and set it aside. Remove the two bolts that hold each brake caliper in place. Remove all four pinch bolts from the bottom of the forks. Remove the axle from the front wheel, then remove the front wheel and set it aside. You might want to inspect the front wheel bearings and clean and lubricate the dust seals on either side of the front wheel at this time.
Other than the front fender, I did not have to remove any Tupperware from the motorcycle during this project.
The piping that delivers fluid to the front brakes is attached to the forks with two bolts on the right fork and one on the left fork. Remove these three bolts. You will need a thin 10 mm open-end spanner to loosen the upper of the two bolts on the right fork – you can’t get a socket in there because the swaged hose fitting blocks access.
Before you go any further with the disassembly (but after you have disconnected the brake piping from the top of the two fork sliders), crack the two socket bolts (hex bolts) in the very bottom of the fork slider loose. You can do this by holding onto the fork slider with your hand and then stuffing a hex key into the bottom of the fork. I was able to crack both bolts loose with a quick snap of my wrist. If you have difficulty, you can partially insert the flared end front axle into the side of the fork down at the bottom and use it to hold the fork leg still when you break the socket bolt loose. Don’t unscrew the bolt any more than necessary to break it loose, otherwise, fluid will leak out.
Larry (Igofar) gave me some very wise advice before I began: “Only remove one fork at a time – never have both forks removed at the same time”. This is important. If you always have one fork installed, you won’t encounter problems later trying to get the front fork lock to engage when you remove the key from the motorcycle. Also, the shiny fork tube is susceptible to damage… if you only have one fork removed at any given time, this lessens the risk of damage to the other one.
Its most efficient if you remove the right-hand side fork first, because this will save a few extra steps when it is time to re-assemble and vertically align the two forks.
Dave D (Dduelin) also gave me some excellent advice. He wrote: “When clean and in the proper lighting at 72,000 miles, I could see a slight 'haze' on the leading side of the fork tube where airborne sand or debris had dulled the chrome. After that discovery, at each fork service I mark or index the fork tube with a piece of tape and a magic marker and rotate it 90 or 180 degrees upon reassembly and even up this minute wear.”
Now, fully loosen the two 12 mm pinch bolts on the right-hand side lower fork clamp. I suggest you loosen the upper one bolt first. Hold onto the shiny fork tube when you loosen the second of the two bolts, to prevent the whole fork assembly from suddenly dropping down.
The chrome surface on the shiny fork tube is fragile. It can withstand most insect impacts, but it can’t withstand banging against another metal surface (like the fork clamps, or your toolbox, etc.). If you nick, scratch, or otherwise damage the chrome surface, your only option is to buy a new fork tube, and that costs about USD $190.00 plus shipping (P/N 51410-MGS-G02).
Disassembling & Draining the Fork
Once you have the fork off the motorcycle, you start disassembly at the top.
Grab the shiny fork tube with your hand and use the 17 mm hex key to unscrew the fork cap from the top of the fork (now you know why you broke it loose before you removed the fork from the motorcycle). It will take about 8 full turns before the fork cap comes off. My experience was that the fork cap only popped up a little bit when it finally disconnected, so I don’t think it is a big safety hazard, but don’t have it pointing at your face when you unscrew it. Refer to the 5:00 minute mark in Jim C-G’s video “Replacing Front Fork Seals & Springs on a ST1300” to see how much movement to expect when the fork cap comes loose.
Once the fork cap has been unscrewed from the fork tube, you need to remove the fork cap from the top of the form damper rod. To get access to the nut below the fork cap, shove a 12 mm open end spanner UNDER the nut, and push down on the end of the spanner to displace the spring collar (the steel tube). Then, put a 14 mm spanner on the nut, hold both spanners in one hand, and unscrew the fork cap with your other hand.
Set the fork cap and the spring collar off to one side and invert the fork over a drain pan to drain it out. Not much liquid will come out – perhaps a little more than half a liter (one pint).
The spring will fall out when you invert the tube, so tip the tube slowly and be prepared for the spring to come sliding out. The ‘spring seat’, which looks like a very large washer, will also fall out into the drain pan – don’t forget to fish it out and set it aside.
While the fork tube is inverted and draining into the pan, you can remove the small socket bolt and its associated copper washer from the bottom of the fork slider. Once the bolt is removed, the whole fork damper assembly will slide downwards into the drain pan.
By now, all the oil that is going to drain out of the fork tube will have drained out, so lay the fork tube / fork slider assembly down on a piece of carpet (so as not to scratch the fork tube) and pull the fork damper out. It will have a silver colour cap on the end (by my fingers in the photo below), remove this cap and set it aside. No further disassembly of the fork damper is possible.
Put the bottom end of the fork damper in the drain pan and pump the rod of the fork damper up and down. It will take a couple of dozen full cycles to get most of the oil out of the inside of the damper. Once oil stops coming out of the damper, turn the whole damper assembly upside down and continue to pump the rod through its full length of travel. Some additional oil will drain out.
Once you have drained the damper as best you can, leave it upside down (thin tube down) to drain in the pan, and pick up the fork slider and tube assembly. Remove the dust seal very carefully, using a dull butter knife.
Dave D. (Dduelin) suggests the following technique: “I learned to use a butter knife to pry the dust seals out. It's less likely to scratch the leg or tube and it's quick. Insert the knife like you were preparing to cut the tube in half and when the blade edge is against the tube I kind of just lift the handle end to twist the blade as a lever and pop the dust wiper out. A small flat blade screwdriver doesn't move the seal much when twisted and the butter knife is dull. The butter knife can also be used to pop the stopper ring out.”
There is a great risk of scratching the chrome surface of the fork tube when you do this, so go slowly and don’t apply too much pressure inwards toward the tube – apply your pressure upwards. You will need to work your way around the dust seal several times to get it loose.
Once the dust seal is removed, you need to remove the stopper ring (a big circlip) that holds the fork seal in place. Once again, be very careful to not accidentally scratch the fork tube with the very sharp ends of the stopper ring. Use the butter knife to get one end of the ring loose, then keep a finger over the loose sharp end as you work around the rest of the ring, prying it loose from the groove that it fits in.
After removing the stopper ring, you can separate the fork tube and its attached components from the fork slider by just pulling the two pieces apart. See the 5:50 minute mark of Jim C-G’s video “Replacing Front Fork Seals & Springs on a ST1300” to see how this is done.
After the fork tube comes out of the fork slider, you can remove the oil seal, the backup ring (looks like a huge washer, bigger than the spring seat), and the smaller of the two bushes by sliding all three parts up and over the top of the fork tube.
Honda’s nomenclature for the two bushes is inconsistent. In the Service Manual, the smaller of the two bushes – the one that fits into the top of the fork slider, just below the oil seal – is labelled ‘slider bush’, and the larger one that clips around the very bottom of the fork tube is labelled ‘fork tube bushing’. In the parts catalog, the smaller one is called ‘bush, guide’ and the larger one is called ‘bush, slider’.
You can then remove the fork tube bushing (the large one clipped around the bottom of the fork tube) by prying it open a wee bit with the small screwdriver and then sliding it over the bottom end of the fork tube. Don’t pry it open any more than necessary, otherwise, you will deform it and you won’t be able to use it if it is otherwise in satisfactory condition.
At this point, you have fully disassembled everything, and the parts look like this if you lay them out on your workbench. Compare the photo below to the illustration on page 15-28 of the service manual.
Now, gather everything up and take the parts inside to your laundry sink. Wash them all using a soft cloth and lots of Simple Green or citrus degreaser. Except for the damper rod, cleaning all the parts is straightforward. Be careful when cleaning the inside surface of the fork slider (the female part of the fork assembly) – that surface must not be scratched, it is as critical as the outer surface of the fork tube. I wrapped a microfiber cloth around the end of a wooden broomstick to clean all the deposits off the bottom inside surface of the fork slider.
Consider using a soft Scotch-Brite pad or fine grade bronze wool (not steel wool) to clean up any corrosion present on the inside top area of the fork slider, where the oil seal, stopper ring, and dust seal fit. Bronze wool is available at most Home Depot stores and at ship chandlers. On my forks, it was evident that water had accumulated in there at some time in the past, which makes a good case for putting some rubber-compatible grease on top of the fork oil seal during reassembly, as suggested in the video “Motorcycle Fork Stiction”.
The damper rod assembly requires a lot of attention, because no matter how many times you pumped it when you had it over the drain pan, there will still be a heck of a lot of old oil and debris inside it. Fill a small cup with a solution of warm water and Simple Green or citrus degreaser, put the bottom end of the damper rod in the cup, and pump. You’ll need to change the solution several times before it remains clean. Pour or spray some undiluted Simple Green or citrus degreaser over the upper end of the rod and pump again – a lot more gunk will come out. Invert the damper rod so that the thin rod is at the bottom, pour or spray some undiluted Simple Green or citrus degreaser into the ‘base’ of the assembly (the part at the top), and keep pumping. It took me about 15 minutes of work to completely clean out the inside of the damper rod assembly.
Once you think you have it as clean as can possibly be, stand it up upside-down on top of a rag (with the narrow rod at the bottom) and leave it overnight. A whole lot more gunk will drain out of the narrow rod overnight. I kind of suspect that this is where the fine granular particles that wear off the sliding surfaces of the bushes accumulate.
Evaluating the Condition of the Bushes
The bushes have a brownish-grey Teflon-like coating on one side, and a copper colour coating on the other side. The condition of the copper colour side doesn’t matter at all, unless the surface is grossly deformed. The copper colour side is fixed, in the sense that it does not move, it stay put. So, if you see evidence of some wearing away of the copper colour, that alone is not a reason to replace the bush (but it does explain where all that debris in the damper rod came from!).
It’s the brownish-grey side of the two bushes that matters – this is the side that slides. On my motorcycle, which had 90,000 km (55,000 miles) on it when I did this work, the Teflon-like coating on both smaller bushes was in fine condition, but the coating on one of the larger bushes was worn away on one side only. Because I had already ordered two of each size of bush, I replaced all of them… but the Service Manual states, on page 15-26, that replacement is only necessary if the bush is scored or scratched, or if the Teflon-like coating is worn away on more than ¾ of the surface.
On the other hand, though, if you have gone to all the trouble of fully disassembling the forks, you might as well replace all 4 bushes. A set of 4 costs USD $25.00 net from Partzilla at the time I write this (that’s about $300.00 Canadian after currency conversion, duties, taxes, and shipping are added), so, for USD $25.00, you can be reasonably assured that you won’t have to fully disassemble the forks for another 100,000 km (60,000 miles) or so – all you will need to do until then is just drain & change fork oil, which is a much simpler & faster process.
Evaluating and Correcting the Condition of the Fork Tube
The fork tube is subject to impact damage from rocks and hard-shelled insects. If it has suffered impact damage, there’s not much you can do about the impact crater, but what you can do is make sure that there are no ridges around the crater that stick up and will damage your new fork seal.
I found a small impact crater on one of my fork tubes. I used a Norton ICE 2000 grit foam finishing disc to abrade away the raised edges of the crater, and followed up by polishing the outer surface of both fork tubes with Meguiar’s Mirror Glaze 9 Swirl Mark Remover. Both are specialty products available from auto body industry suppliers, they are not usually found at consumer retail stores. Fine grade bronze wool (not steel wool) could also be used.
There’s no point in perfecting the condition of the fork tubes, only to scratch them up when re-installing them, so take a moment to clean the inside of both the upper and lower fork clamps (still on the motorcycle) with a soft 3M Scotch-Brite pad, bronze wool, or similar gentle abrasive before you put the forks back on the motorcycle.
Putting it Back Together
Re-assembly of the fork and installation back on the motorcycle is quite straightforward and easy to do.
Lubricate the landings on the inside surface of the fork slider where the smaller bush, the backup ring, the oil seal, and the dust seal will go. I used rubber-compatible grease as the lubricant.
Lubricate the inside of the larger of the two bushes and install it on the bottom of the fork tube. Lubricate the outside of that bush, then install the fork tube into the fork slider.
Lubricate both sides of the smaller bush, lubricate the entire surface of the fork tube, then slide the smaller bush down the outside of the fork tube. Seat it in its groove using the genuine 85¢ Home Depot Honda ST 1300 fork bush seating tool. It’s easy to tell when it is properly seated by just looking into the top of the fork slider. Not much force is needed.
Install the backup ring. Don’t forget to install the backup ring. It is easy to forget to install the backup ring, don’t ask me how I know that.
Now, install the fork oil seal. Honda includes a little fortune-cookie like slip of paper telling you to install the fork oil seal with the manufacturer lettering facing up. To determine which side has the manufacturer lettering on it, just find the closest scanning electron microscope to your home and take the new fork seal there to examine it under the microscope. Failing that, the side of the oil seal that has the little square dimples embossed in it is the same side as the side with the manufacturer lettering.
In Delboy’s video “How To Replace regular type fork seals”, he suggests cutting up a plastic milk jug to use to protect the new seal when you slide it down the fork tube. An equally effective method is to use the plastic wrapper that the new fork seal came in to protect it as you slide it down the tube.
Use the Home Depot tool to seat the fork oil seal. Instead of ramming the tool down on the fork seal and risking deformation of the new seal, just press down hard on the tool and the seal will slip into place – assuming, of course, that you lubricated the inside of the fork slider where the seal seats.
The stopper ring (big circlip) will almost certainly be corroded. Clean it up with some bronze wool, then wash it thoroughly with soap and water to get rid of any bronze wool residue. Slide it down over the fork tube, put your finger over one end of the ring (to prevent it from scratching the fork tube), and poke the other end into the top of the fork slider using your other hand. Press the ring all the way down into place with the Home Depot tool. Visually confirm that the ring is fully seated through 330° in the groove within the fork slider.
If you choose to add some rubber-compatible grease on top of the seal and stopper ring, do it now, before installing the dust seal. Don’t add too much, because the dust seal almost completely fills the remaining space in the top of the fork slider.
Install the dust seal. Put a little bit of lubricant on the fork tube before you attempt to slide the dust seal down the tube.
Find the silver cap (‘oil lock piece’) that fits on the end of the fork damper and re-install it. If you put a wee bit of rubber-compatible grease around the base of the fork damper before you install the oil lock piece, it won’t fall off when you lower the assembly into the fork tube.
Lower the fork damper assembly into the fork tube. Apply a little bit of low-strength Honda blue threadlocker to the fork socket bolt (hex bolt) that goes in the bottom of the fork slider to hold the fork damper in place, then install the bolt and torque it to 20 N·m (14 foot-pounds). You might have to hold the nut at the very top of the fork damper to prevent the damper from rotating when you tighten the fork socket bolt… I didn’t have to, the bolt tightened nicely without any need to hold the fork damper rod.
Take it easy when applying the threadlocker to that bolt. Make sure you are using low-strength threadlocker. Later, when you put the axle in place, that bolt can’t escape, so all you are doing with the thread locker is ensuring that it doesn’t wiggle loose and let the fork oil escape. Chances are that you will be the person who next removes that bolt in another 60,000 miles… so, don’t make your future life difficult.
Adding the New Fork Oil
Stand the fork assembly upright. Lift the damper rod up so you don’t get it coated in oil when you add the oil.
Pour a little bit of oil – perhaps a few ounces (100 ml) – into the fork, and then firmly push the shiny chrome fork tube down to the very bottom of the cast aluminum fork slider. Then, pour more oil into the fork until the oil level is about 4 or 5 inches (10 cm) below the top of the fork tube. That’s less than the final fill amount, which will be added later.
Now, operate the fork damper rod through its full range of motion at least 20 or 30 times. Be sure to push it all the way down – you will encounter some resistance about an inch from the bottom, don’t confuse that initial resistance with being the bottom limit of travel. After you have operated the fork damper rod 20 or 30 times, the motion should be smooth all the way up and down. The resistance will be different between the upstroke and downstroke, that is normal.
Now operate the chrome fork tube several times through its full range of motion, again being sure to hit the bottom on the way down. Finally, operate the fork damper rod once again, to confirm smooth operation through its full range of motion. You want to be certain that there are no air bubbles remaining anywhere in the bottom of the fork slider or within the fork damper rod assembly.
Honda’s specification is that the fork oil level should be 62 mm (a tiny bit less than 2 ½ inches) from the top of the fork tube when the fork tube is fully compressed into the fork slider. This is measured without the fork spring or the spring collar (steel tube) in place. It doesn’t matter where the fork slider rod is when you carry out this measurement, it can be in any position.
So, get your syringe with the 62 mm tube attached to it ready on the bench next to you, then pour fork oil into the fully compressed tube until it is about 2 inches (50 mm) from the top, then use the syringe to suck out the excess. Once you have done this, verify the 62 mm from the top measurement a second time using a different method (e.g. a ruler, or a pencil with a tape mark around it at 62 mm).
Closing up the Fork
Before you begin closing up the fork, you need to get some tools and components in place close by on your workbench.
Find the fork cap and install the new O-ring on it. Lubricate both the threads and the O-ring with fork oil before installing the O-ring. Place that assembly within reach.
Get the fork spring, the spring seat (smaller of the two ‘big washers’), and the spring collar (steel tube) within reach on the workbench. Get the 17 mm hex key installed on a torque wrench set to 20 N·m (14 foot-pounds). Place the 12- and 14-mm open end wrenches within reach on the workbench.
Pull the damper rod up as high as it will go and hold it up until you are ready to install the spring and spring seat (the rod will slowly sink down if it is not held). Extend the fork tube upwards until it reaches the top of the fully-extended damper rod.
Pick up the spring and the spring seat and place the spring seat on the top of the spring. Tilt the whole fork assembly sideways to about a 45° angle (this to avoid splashing when the spring slides down into the fluid) and drop the spring and spring seat into the tube. The pointy end of the spring (the tightly wound end) goes downwards. The spring goes in first, with the spring seat on top of the loosely wound end (big end) of the spring. As soon as you have dropped the spring and spring seat in, grab the top of the damper rod before it sinks down out of sight.
Press the fork tube down a few inches into the fork slider. Lift the damper rod up as high as it will go. Hold the damper rod up by sticking a finger in between one of the coils of the spring. Now install the spring collar (steel tube) over top of the damper rod. Grab your 12 mm open end wrench and stick it UNDER the 14 mm nut on the damper rod. Pry up the rod a bit (in effect, you compress the spring a bit) and hook the mouth of the 12 mm wrench over the far side of the spring collar.
Pick up the fork cap and spin it onto the threads of the damper rod. When it comes time to tighten it up, pick up your 14 mm wrench and install it around the nut in such a way that you can hold both the 12- and 14 mm wrenches in one hand. Now grab the torque wrench with the 17 mm hex on it and tighten the fork cap against the nut until 20 N·m (14 foot-pounds) of resistance is achieved.
Dave D wrote: “If someone adds preload with longer spacers or extra washers, it may become difficult to press the fork cap down and turn it to engage the threads of the cap and tube. There have been folks posting they couldn't do it alone and/or had great difficulties here. I advise them to press down the threaded cap using a ratchet or breaker bar with the 17 mm hex, hold the cap still, and with the other hand turn the tube to engage threads instead of trying to turn the cap and holding the tube still. It's simple but it works.”
Grab the spring collar with your hand, compress it slightly, and remove the two open end wrenches. Don’t let the fork cap, with its very fine and soft aluminum threads, slam against the top of the hard steel fork tube. Gently release the pressure you have been holding on the spring collar, and spin the fork cap – by hand, not with the wrench – into the threads of the fork tube. Screw the cap on all the way until the O-ring disappears into the fork tube, but don’t attempt to tighten it up solidly – the final torque will be applied to the fork cap once it is installed on the motorcycle.
Re-installing the Fork
Check the upper and lower fork clamps on the motorcycle and confirm that they are clean inside and that the three bolts (one on the top clamp, two on the lower clamp) are loose. Put a 12 mm socket on the shortest ratchet handle you have, then take the (right-hand) fork and the wrench over to the motorcycle. Insert the fork up into the two clamps until it is “approximately equal” (eyeball equal is good enough at this stage) in vertical alignment to the other fork. Don’t worry about being exact. Gently & lightly snug up the two bolts on the lower clamp just enough to prevent the fork from sliding downwards onto the floor. Don’t over-tighten the bolts – all three of these fork clamp bolts are steel bolts that fit into a much softer aluminum casting. Don’t be concerned about correct torque at this time, the right fork installation is temporary at this stage of the process. Don’t tighten the upper fork clamp bolt, it needs to remain loose.
The Other Fork (the left-hand fork)
Repeat the whole process on the other fork. It took me about 3 hours to do the first fork, and about 45 minutes to do the second fork. Once you have seen the first fork fully disassembled, you know what to expect with the second fork and the process becomes very simple and straightforward.
Re-install the second fork (the left-hand fork)
The process for re-installing the left-hand fork is the same as the process for re-installing the right-hand fork, except that you want to be more meticulous about getting the vertical position of the second fork correct.
The Service Manual doesn’t give a specification for how much the fork tube should stick up above the upper fork clamp. I chose to set the top of the left-hand fork tube 1 mm above the top surface of the upper fork clamp, this to reduce the risk of water puddling at the junction of the fork cap and fork tube.
Once you have the left-hand fork installed at the correct vertical height (relative to the upper surface of the top fork clamp), gently snug up the two bolts on the left side lower fork clamp. Again, don’t worry about correct torque right now, and don’t overtighten them.
To ensure perfect vertical alignment of the two forks, see this suggestion: Fork Vertical Alignment.
Now, install the axle partway through the right-hand side fork, loosen the lower fork clamp bolt holding the right-hand fork in place, and vertically align the left and right forks, using the axle as the reference point for vertical alignment.
Check to make sure that the vertical alignment of the top of the fork tubes “makes sense” above the upper fork clamp. The two fork tubes should protrude an identical amount, within 1 mm tolerance. Then, snug up the two bolts on the lower fork clamp of each fork. Don’t worry about correct torque at this time, these bolts will be loosened later.
Final Tightening of the Fork Cap and Upper Fork Clamp Bolts
The next step is to apply correct and final torque to the fork cap and the upper fork clamp bolts.
Because all the various bolts (about a dozen of them) in the fork system and the front brake calipers are safety-critical and need to be torqued to specific values, I suggest you get a small bottle of ‘White-Out’ or some other paint-on correction fluid, and use that to mark a bolt once you have applied the correct final torque to each bolt. If you want to use a product that is specifically manufactured for torque inspection, you can get a small tube of Dykem Torque Seal or similar from a specialty shop.
Check to make sure that the single 12 mm pinch bolt on each side of the upper fork clamp is completely loose. Now use your torque wrench with the 17 mm hex installed to tighten the fork cap to achieve 23 N·m (17 foot-pounds) of resistance - the two lower fork clamp pinch bolts that you snugged up earlier will prevent the fork tube from rotating. It might be a good idea to put a towel or pad over the gas tank before you start, just in case you drop the wrench, or it slips out of the fork cap when you are torquing it.
Once you have the two fork caps correctly torqued, apply final torque to the pinch bolt on the upper fork clamp on each side. This is a 12 mm bolt and the specification is 26 N·m (20 foot-pounds).
Finally, mark the fork caps and the two upper pinch bolts with the Torque Seal paste or with correction fluid to indicate that you have applied final torque to these items.
Aligning the Front End (Steering and Forks) of the Motorcycle
Delboy produced an interesting video titled “How To Re-align Motorcycle Forks the Easy Way". In this video, he shows how the front end of the motorcycle can become misaligned, and how to correct it.
If you are interested in carrying out this alignment procedure, now is the time to do it, because the only fasteners that you have applied final torque to are the two upper fork mount pinch bolts. If you are not interested in following Delboy’s procedure, skip ahead to the next section “Not Interested in Delboy’s Alignment Suggestion? Want to do it By the Book?”
- Install the front wheel and manipulate the brake calipers onto the front brake discs. Insert the axle and install the large 22 mm bolt into the right end of the axle. Tighten the bolt sufficiently to pull the axle fully through the forks, using your 17 mm hex to stop the axle from rotating while you do this. Don’t apply final torque to the front axle bolt at this time.
- Install the three bolts that attach the piping for the front brakes to the top of the fork sliders, but leave them loose.
- Completely loosen up the two pinch bolts on each side of the lower fork clamp.
- Install the two brake calipers onto the fork struts. Each caliper has two fasteners (hex head for the left side, 12 mm bolts for the right). The left caliper pivots in daily use (to operate the secondary master cylinder), take a moment to clean up, inspect, and lubricate the bearing at the lower mounting point of the left brake caliper and the bracket at the upper mounting point of the left brake caliper.
- The service manual calls for new fasteners to be used at all four locations that hold the two front calipers in place, but in practice, many of us simply clean up the old fasteners to remove remnants of old threadlocking compound and apply new low-strength threadlocker to these fasteners. The torque specification for all four caliper fasteners is 31 N·m (23 foot-pounds). Mark each fastener with Torque Seal paste or with correction fluid once you have applied final torque.
- If you want to follow Delboy’s procedure for front end alignment, confirm that the axle is fully inserted into the left fork, tighten the two pinch bolts at the bottom of the left fork (only the left fork, the right pinch bolts remain loose) to 22 N·m (16 foot-pounds), then tighten the axle to final torque specifications of 78 N·m (58 foot-pounds). Once the axle has been torqued to final specifications, torque the two right axle pinch bolts to 22 N·m (16 foot-pounds), and loosen up the two left axle pinch bolts (the pinch bolts that you previously torqued to 22 N·m (16 foot-pounds). Mark the axle bolt and two right pinch bolts with Torque Seal paste or correction fluid.
- Final torque has been applied to the fork caps, the single pinch bolt on each side of the upper fork clamp, the two fasteners holding each brake caliper in place, the axle, and the two axle pinch bolts at the bottom of the right fork.
- The following fasteners are completely loose – all four fasteners on the lower fork clamp, the axle pinch bolts at the bottom of the left fork, and the three bolts (two on the right, one on the left) holding the front brake piping to the top of the fork sliders. The front fender and fork brace (if you use an aftermarket fork brace) have not yet been installed on the motorcycle.
7. Now, mount the motorcycle and bounce the front end up and down several times as shown in Delboy’s video “How To Re-align Motorcycle Forks the Easy Way".
8. Once you have done this, tighten the four bolts on the lower fork clamp and the two axle pinch bolts at the bottom of the left fork in the manner Delboy suggests, which is to tighten each bolt about ¼ of a turn at a time, working around the six bolts in circles. Once they are ‘hand tight”, snug them all up in a circular manner.
9. Applying final torque of 26 N·m (20 foot-pounds) to the four bolts on the lower fork clamp is a complex and repetitive procedure. Because each of the two bolts on any one side of the lower fork clamp tightens the same casting, when you apply final torque to the second bolt on one side, you will discover that the first bolt on the same side that you correctly torqued is now loose. You will need to go back and forth between the two bolts on the same side about 3 times before achieving final torque on both bolts. Mark these 4 fasteners with Torque Seal paste or correction fluid.
10. Apply 22 N·m (16 foot-pounds) torque to the two axle pinch bolts at the bottom of the left fork slider. Again, you have two fasteners acting on the same casting, so you will need to go back and forth a few times to achieve the correct torque on both bolts of each side. Mark these fasteners with Torque Seal paste or correction fluid.
11. Apply final torque of 12 N·m (9 foot-pounds) to the three fasteners that hold the front brake piping in place at the top of the fork struts and mark these 3 fasteners with Torque Seal paste or correction fluid.
Not Interested in Delboy’s Alignment Suggestion? Want to do it “By the Book”?If you are not interested in following the alignment procedure suggested by Delboy, and want to reassemble the front end as Honda directs on pages 15-32 and 15-33 of the Service Manual, proceed as follows:
- Install the front axle (without the front wheel) and front axle bolt, tighten the bolt finger-tight only.
- Tighten the four lower fork clamp pinch bolts to 26 N·m (20 foot-pounds).
- Tighten the three fasteners that hold the front brake piping in place at the top of the fork struts to 12 N·m (9 foot-pounds).
- Follow the installation instructions for setting final torque on the fasteners at the bottom of the front wheel, which are published on pages 15-20 and 15-21 of the Service Manual. Post #3 in the discussion “Wheel Torque Specs - ST1300” summarizes the procedure.
The last step in the re-assembly process is to re-install the front fender. It is held in place by six fasteners. Honda does not specify a torque for these fasteners, therefore, “standard” torque based on the fastener size (listed at the top of page 1-13 of the Service Manual) are used.
If you use an aftermarket fork brace, install it now, after everything is back together, but be very critical when observing the fit of the fork brace when you put it into place. If it does not fit around the top of the fork sliders “perfectly”, with no friction or movement of any kind of the forks when you put it in place, you might just want to leave the fork brace off your motorcycle for your next few thousand miles of riding, and see what you think of the handling. I say this because if the width between fork vertical centerlines of the aftermarket fork brace is off by as little as one-thousand of an inch, it will introduce stiction to the front fork system that you just painstakingly overhauled, which may cause uneven wear of the bushes within the fork.
Final Safety Check
As mentioned earlier, all the fasteners used on the front forks and front brake are safety-critical. In the aircraft maintenance industry, all safety-critical fasteners must be double-checked by a second qualified person before the aircraft is released to service following maintenance. An “almost just as good” way of verifying nothing has been missed is to leave the motorcycle overnight, then double-check it the next day. Here’s the checklist, from the top down:
1. Fork caps (1 each side), top fork clamp pinch bolts (1 each side),
2. lower fork clamp pinch bolts (2 each side),
3. brake fluid pipe attachments (2 on the right, one on the left),
4. brake caliper attachment bolts (2 per caliper),
5. axle bolt (1 only on the right side),
6. front axle pinch bolts (2 each side),
7. front fender attachment bolts (3 per side).
I hope this post is useful to others in the future, and once again, I thank Larry, Dave, and Jim for the contributions they have made in the past, without which I would never have have had the knowledge and confidence needed to overhaul the forks on my motorcycle.
Michael
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And will be my go-to resource the next time I do it. Great job!
