Fork Legs different length

[mrbug]

I finally got the seals, fluid and bushings replaced in my forks. After I put the forks back on the bike, I noticed that the right leg is 1/8" longer than the left as measured from the lower triple tree clamp. I have not put the wheel back on yet. Both legs are setting flush with the top triple tree clamp. I have taken them back apart and can not figure out what is causing it and don't have any spare parts laying around. I never noticed it before when changing tires but wasn't looking for it either. Surely this is not normal or will putting the wheel back on and putting it back on the ground fix the problem?

 

[bdalameda]

Where are you measuring to - the center of the axle? or somewhere else? I have seen this before - it usually is a shim or spacer in the wrong place. A slight difference if everything is put together correctly is really not an issue as the entire assembly when the wheel is installed and everything is tightened up - will come into perfect alignment. When the bike is sitting on the forks and the springs are compressed the fork tubes and axle will be aligned just fine. The only time the mis-alignment is seen is when the tubes are unloaded and the front axle removed. I noticed that my St1100 is slightly mis-aligned when I remove the front axle and it has not caused me any issues. It is not 1/8 out though maybe 1/16.

 

[mrbug]

I was measuring to the center line of the axle. I realize that I am measuring with a standard tape measure to a spot in space from an non machined surface. The forks are quite simple and that is what really puzzled me. Thanks.

 

[John OoSTerhuis]

Brad. Assuming a non-ABS ST1100, is the right fork bottom bolt (up inside the axle hole on the slider) torqued to spec? Correct amount of threads showing (10.5mm) on the end of the damper rod connected to the fork cap?

Are the fully-assembled forks the same height when off the bike and standing side-by-side?

Just thinking out loud, I guess; I really can't imagine much that could be wrong though and would put this in the category or normal variances. IMHO, I'd pop the forks on and GO RIDE!

John

 

[two_wheeled]

You probably don't want to reassemble them all over again but that doesn't sound right to me. I'd take them both apart again and make sure all the internal bushings and spacers are in the same place. Or you could try to ride on it, but don't be surprised if people start calling you 'lefty'.

 

[wjbertrand]

I wonder if one of the damper rods is not fully seated into the base of the lower leg casting? I seem to recall an issue with another ST that was having an instability problem that was traced to this assembly error.

 

[dwalby]

I wonder if one of the damper rods is not fully seated into the base of the lower leg casting? I seem to recall an issue with another ST that was having an instability problem that was traced to this assembly error.

Jeff, are you saying that its possible to torque down the bolt that holds the damper into the lower fork slider, without it being in the right position internally, and not notice that anything is wrong? I would have thought that the bolt wouldn't even thread into the damper if it were out of position by that much. And if its in position but the bolt isn't tightened enough, I'd expect oil to leak out the bottom through the threads.

I'm not challenging your reply, I'm just asking for a little more clarification on the assembly error so I know what to look for the next time I replace my seals. I never noticed anything difficult putting that bolt back in, so I'm curious as to how you could do it wrong.

 

[wjbertrand]

^^^
I'm not sure how this could happen either Doug, just recalling an earlier post that seemed to describe this problem. Since there's a seal washer under the head of that lower bolt, it shouldn't leak as long as it's tight.

 

[mrbug]

I wonder if one of the damper rods is not fully seated into the base of the lower leg casting? I seem to recall an issue with another ST that was having an instability problem that was traced to this assembly error.

On my 01' non abs bike, the right leg is the only one with a damper inside of it. Both legs are completely different on the inside. On the right leg, the nut screws into the chrome fork tube and onto the end of the damper rod. On the left leg, the nut screws only into the fork tube.

 

[dwalby]

On my 01' non abs bike, the right leg is the only one with a damper inside of it. Both legs are completely different on the inside. On the right leg, the nut screws into the chrome fork tube and onto the end of the damper rod. On the left leg, the nut screws only into the fork tube.

Agreed, but we're talking about the other end, the part that sits in the bottom of the lower tube, and is held in by the bolt that you have to remove through the access hole in the bottom of the fork lower tube. If you replaced the seals then you had to have removed it to pull the upper slider out of the lower tube.

Technically both tubes have dampers, the right one uses a cartridge style damper, the left one uses the older dampening system which forces oil through an orifice hole.

 

[mrbug]

Brad. Assuming a non-ABS ST1100, is the right fork bottom bolt (up inside the axle hole on the slider) torqued to spec? Correct amount of threads showing (10.5mm) on the end of the damper rod connected to the fork cap?

Are the fully-assembled forks the same height when off the bike and standing side-by-side?

Just thinking out loud, I guess; I really can't imagine much that could be wrong though and would put this in the category or normal variances. IMHO, I'd pop the forks on and GO RIDE!

John

Imagine what I can learn if I would read. I noticed that dimension on the right side. I checked mine and there is NO way to ever get 10.5mm of thread. With the jam nut screwed all the way down, I could only get a tick over 8mm. I did chuck the nut up in the lathe and turn it down so I could get the 10.5mm min. the manual calls for. I am going to try to order another one, I just wanted to see if it would work. It did not change anything. I did notice one thing, the nuts have different flange thicknesses and I was lining them flush with the top of the triple tree. This time I lined them up using the bottom of the flange instead and they are now closer together. I am saying screw it and putting it back together. I really think they have been this way since I had the bike.

It has been an interesting discussion and thanks to all for your help.

 

[dwalby]

Imagine what you can learn if you read. I noticed that dimension on the right side. I checked mine and there is NO way to ever get 10.5mm of thread. With the jam nut screwed all the way down, I could only get a tick over 8mm. I did chuck the nut up in the lathe and turn it down so I could get the 10.5mm min. the manual calls for. I am going to try to order another one, I just wanted to see if it would work. It did not change anything. I did notice one thing, the nuts have different flange thicknesses and I was lining them flush with the top of the triple tree. This time I lined them up using the bottom of the flange instead and they are now closer together. I am saying screw it and putting it back together. I really think they have been this way since I had the bike.

It has been an interesting discussion and thanks to all for your help.

Hmmm, thinking about this a bit more, the dampening rod is under tension from the spring preload, so its extended fully up with the fork cap off. You then screw the fork cap onto the threads on the dampening rod, and this determines the final height of the fork cap, thus the overall length of the fork, because the upper slider tube then slides up to mate with the fork cap for the final assembly. So if you are only able to get 8mm of threads into the fork cap, that means your overall length will be 2.5mm too long, which is right about at your 1/8" extra length on the right fork. Not sure why it wouldn't have changed after you trimmed the nut thinner to get the 10.5mm thread extension, that should have dropped the final height of the fork cap by 2.5mm relative to the bottom of the fork.

Edit: you did remember to tighten the fork cap against the top of the nut on the damper rod first, before bringing the slider tube up, so that the 10.5mm adjustment couldn't move while attaching the cap to the top slider tube.

 

[mrbug]

Yes and actually I screwed the nut down past the 10.5mm dimension by about .02". What I don't understand is why Honda would have put in that dimension (Thanks to John for pointing that out) if it didn't really apply? I have a buddy that rebuilds dirt bikes, (engines & suspensions) and we have been debating that very thing for the past couple of days. I may play around with it some more when I get back from the Cape Fear Rally.

 

[mrbug]

Hmmm, thinking about this a bit more, the dampening rod is under tension from the spring preload, so its extended fully up with the fork cap off. You then screw the fork cap onto the threads on the dampening rod, and this determines the final height of the fork cap, thus the overall length of the fork, because the upper slider tube then slides up to mate with the fork cap for the final assembly. So if you are only able to get 8mm of threads into the fork cap, that means your overall length will be 2.5mm too long, which is right about at your 1/8" extra length on the right fork. Not sure why it wouldn't have changed after you trimmed the nut thinner to get the 10.5mm thread extension, that should have dropped the final height of the fork cap by 2.5mm relative to the bottom of the fork.

Edit: you did remember to tighten the fork cap against the top of the nut on the damper rod first, before bringing the slider tube up, so that the 10.5mm adjustment couldn't move while attaching the cap to the top slider tube.

I finally got around to playing with the forks again last night. I ended up taking them back apart and putting them together. Everything came out the same as before. I ended up running the nut down on top of the dampening rod until I got the forks the same height. The final thread length ended up at about 12.5mm vs. 10.5mm as stated by Ma' Honda. There was definitely something off because my front fender started making a popping sound when I turned the front forks. That has gone away now and there doesn't appear to be any abnormal wear from riding it 2000 miles like that. As much as the wind was blowing, I spent most of the time on the sidewall anyway.