ST1100 hard to push out of garage after sitting Awhile

Joined
Aug 24, 2012
Messages
126
Location
Moon, VA
Bike
1991 ST1100
STOC #
8654
Hi,

We had an unusually warm weekend, so I got my 1991 ST1100 out for a ride. The bike almost required another person to push the bike out of the shed. I live on the coast, and things tend to oxidize quickly.

Is there anything that can be applied to rotors to help slow the rust from forming? It rubs off after a short ride.
 
Joined
Jan 8, 2011
Messages
7,062
Location
Arizona
Bike
2007 Honda ST1300A
My old Bonneville's or Norton's rotors would be red with rust (and this was in Arizona) overnight! Like you said, once you applied the brakes it cleans them off.
You don't want to put anything on the rotors themselves.
.02
 
Joined
Dec 27, 2004
Messages
829
Location
Medina, Tennessee
Bike
2021 Tracer 9GT
STOC #
375
Hi,

We had an unusually warm weekend, so I got my 1991 ST1100 out for a ride. The bike almost required another person to push the bike out of the shed. I live on the coast, and things tend to oxidize quickly.

Is there anything that can be applied to rotors to help slow the rust from forming? It rubs off after a short ride.
Ah coastal living, don't you just love it? Your disks are just going to corrode due to the high iron content and salt air, and there is not much you can do about it other than keep it inside, keep it clean and just ride it. But, your pistons are sticking on at least one caliper due to crud on the pistons and corrosion on the disk. Take the calipers off, remove the pads. Pull them apart, clean them up and grease the slider pins with brake specific grease. Push the pistons out ever so slightly with the brake lever/ pedal and scrub thoroughly around each piston with a household cleaner and a toothbrush. Push the pistons back in, put the calipers together and and replace the pads. You should be good. If not, you may need to replace some pistons and seals, but I doubt it. I always clean the disks with a rag and brake parts cleaner after changing a tire or working on the brakes, wear gloves and eye protection.
 
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mikew1231

Mike W.
Joined
Jan 6, 2008
Messages
65
Location
Tracy, Minnesota
Bike
ST1100
STOC #
7245
Greetings!
One of the guys I work with gave me this today, and I just have to share. It's geared towards a dirt bike, but the article or rant or whatever is quite good. I'll paste it here, I'm sorry I can't acknowledge the author as I don't know who wrote it.

FRONT BRAKE PROBLEMS
Common problems are; Spongy! Springy! & Draggy!
You have ridden the bike a couple years, have a vague recollection that the brake used to be real good and now it really sucks?
Your Buddy can do two finger stoppies and you can't get your front brake to slow you down when backing the bike outa the pickup?
Common ailments are:

l : Spongy:
You spend a little time upside down and when you get up the brake is junk? You can push on the caliper and the brake comes back, until it gets on its side ?gain or

2: Springy:
The brake just does not have sufficient power; you have bled the brakes till your brain hurts yet the brakes feel Spongy! That may be "Springy?'

Or

3: Draggy:
When you release the brake it continues to drag? Or you are riding along and the brake seams to apply itself? (That's Draggy)

For starters lets study the principles of the system from the top:
First your fingers apply pressure to the lever, the lever has about a 5 to I ratio and it pushes on a piston, the area of the piston on my KTM factored against the area of the two caliper pistons is about a 13 to I ratio. Multiply that by the lever ratio and you get about 65 to I times say 20 lbs pressure at the lever equals 1,300 lbs per sq. inch on the pad. That pressure is how they stop the bike with such small brake area! The use of fluid to transfer this pressure to the wheels makes for a solid connection that can cope with suspension movements, problem is the brake can get hot and most fluids boil at reasonably low temps so brake fluid is special stuff that can deal with the heat. Back to that word "solid", important to understand fluid does not compress, but air does!
Thus any air in the hydraulic system equals
"Spongy"!
Let's try to understand these points about brake fluid. Water or even "coolant" have way too low of boiling point, oil and rubber don 't always get along but by matching the right components they can. Brake parts need rubber so some fairly specialized fluids have been developed which must be compatible with both the rubber parts and the heat. The stufT that they put in brake fluid to raise the boiling point also make it hydroscopic, thus it tries to absorb water, Now this brake fluid attracts moisture so effectively that if it is exposed to air it will suck the water out of the air, once it has the water in the brake fluid it is capable of boiling and when it does that you brakes turn to mush!
The Master Cylinder (MC) has a reservoir (Res), at the top of the Res is a diaphragm, the purpose of the diaphragm is important! Its job is to separate the brake fluid from the air yet allow the fluid level to go up and down as we work the brakes, as they the fluid level goes down as the brakes self-adjust for wear and up as the brake fluid heats up with use.
That piston in the MC has a spring that holds it out against the lever when the brake is released; in this position the piston has uncovered a "port" from the MC bore to the Res. This is important, every once in a while we find some guy has bought a lever for an "X" and put it on his ' 'Y" and his brake does not release. What is happening there is lever "X" is holding the piston in a bit, that port is covered and if the brakes generate a bit of heat the wheel locks up and rider does a "face plant", just in front of the bike. Try to avoid this.
Next I want to talk about friction surfaces. The brake lining is stuff that has been developed that will wear well while creating friction and cope with heat. The rotor is metal, cast iron make great brakes but is ugly on a motorcycle application so we mostly have stainless. This stuff is tough but has one problem, with use it gets shiny! Next time you're at the auto parts store take a look at a new rotor for a car. It has a ground texture with a cross grain. Now walk thru the bike shop, you will see the same pattern only much finer! The reason is the car piece is cast iron and it leaves a very course finish when machined but this cross grain is desirable! Reason is it shears off a small amount of brake lining each time you apply the brakes. Don't worry about running out of lining, which is the least of our worries, what we worry about is the friction surface getting polished shinny smooth from use so that it is no longer shearing off friction material. Then the pressure required to make the brake effective goes way up and the friction instead of stopping the bike just polishes the rotor more problem gets worse! When that lining is being sheared off it is letting heat out! Watch the professional drag races on TV, when they put the camera inside John Force's car there is a black smoke inside (tire smoke is blue) that is clutch lining. Every run they regrind all of the clutch parts to maintain that cross grain so the next run it will shear the same amount of lining off. Once the parts, brake rotors or clutch plates become "Glazed" they lose coefficient. of friction thus requires more pressure and they retain heat within them.

Springy!
What makes "Springy" difficult is we can't tell it from Spongy! !? But they are different.
Now in the interest of keeping your bike more nimble than your car the front caliper is made light! Light means some flex. I can measure caliper flex of .010" on my KTM. So .010" X 65 (ratio we figured out earlier) the lever should move .650" or about 518th inch of "springy" This is normal! Don't gloss over this part! A lot of what we think is Spongy is Springy! The answer here is the coefficient of friction of the brakes friction surfaces has been lost due to glazing of that darn stainless rotor! When the bike was new we apply the brake, two fingers is fine, the co-efficient of friction is sufficient to slow the bike. Now the bike is two years old and we are cycling new linings, hoses, Master Cylinder, even reading on the internet trying to get it back to like new and noting seems to work.
When the brakes are well used the rotors become glazed which is an almost chrome like surface the coefficient of friction goes away, more pressure is required at the friction surface which means much more pressure at the lever to generate the needed stopping power. That extra or excess pressure makes that light weight caliper flex, thus our brake feels spongy but in reality it is springy!
The fix is not to complex, first, assuming we have sufficient brake lining thickness I am going to take the brake lining out, lay a piece of course sandpaper on the bench, lay the brake pad on it face down and give it a couple of scrubs. This will get us thru the glaze on the lining!
Next we need to remove the wheel; I put the axle in the vice so I can put the wheel on it and spin it. An option is to do this on the bike but we have to take it on and off a couple times so the vice is easier if you have one. Then I unbolt the rotor; flip it so the back side is up. Next I am going to take a disc sander, I use about 40 grit and give the wheel a slight spin and apply the sander to the rotor. If you hold the sander at the right angle it will make or maintain the wheel spin, we don't need or want much speed and in a matter of a few revolutions we have a rotor that has the desired cross grain of a new one, on that side. Then I flip the rotor back, Loctite & torque the bolts etc. Then surface the outside. The object here is to scuff thru the glaze, leave a texture but not grind the rotor down too much to where it could become irregular. Unless your rotor is trashed this should restore your coefficient of friction to near new!
With friction restored pressure required to make the brake effective will be so much lighter that you will be flexing the caliper much less and the brake will be more effective and feel better!

Spongy:
Spongy is air in the system, very common and unbelievably hard to get ALL of it out. The air is likely to hang out in a couple areas:
l : On the KTM's there are "Banjo" fittings on each end of the line attached with "Banjo bolts". The banjo bolt has a hole thru the center and one out from the center. It should have two or three out from the center, otherwise depending on the direction that hole is facing it may hold an air pocket. I am a firm believer in taking those banjo bolts to the vice and adding one or two holes so no matter what direction the bolt ends up with facing up an air bubble will rise to the top. 2: Next is that point in the brake hose where it is higher than the master cylinder! 3: The other is in the caliper the piston bores. They are round and sideways in relation to the bike. The bleed screw is on top yet no matter how much "Bleeding" you do it is very possible that a small bubble is being maintained in the upper part of one of those bores. As the brake lining wears down more of the pistons protrude out of the bore that bubble gets longer, thus the compress able area is larger. So if you bought new linings and your brakes got better? Then you just made the air bubble smaller? A common story, and a crutch that a lot of riders rely on is to press their knee against the caliper to push it in which in turn pushes the pistons in and forces the fluid back to the top and often flushes air in the system back to the reservoir. If that helps your brakes you have air in the system and just moved it to the top, better but not fixed! Let's set a goal here that there be zero air in the system! This is trickier than meets the eye!
This is how I do it on a off road bike with a two pistons on one side type caliper, an opposing piston deal such as a street bike may have will be more complex. We are going to need at least a pint of fluid before we are done, I would buy a quart.
First without breaking any fittings loose lets remove the entire system from the bike, Next I clamp the master cylinder in the vice by its mount so the reservoir cap is up, flat & level. The caliper is a couple down the bench, lower only by the height of the vice and I have trays at both places because I am going to make a mess. The hose is routed so it does not have any point higher than the master cylinder. Remove the brake lining and set them aside where they will not get contaminated with fluid, take a can of brake clean and a tooth brush and clean very thoroughly around the pistons. Then we lay the caliper piston side up. Remove the top of the MC reservoir, set the cap aside, make certain the reservoir is full, and now pump the lever while monitoring the caliper pistons. If one comes out and the other stays in use a "C" clamp to stop the one coming out after it is maybe 1/2 inch exposed so you get them fairly evenly out. What we want to avoid is having one out and not having the hydraulic system to help with the other. Keep the reservoir full and continue pumping and loosen the clamp(s) as needed so you get both pistons out. Now clean the pistons with a rag and set them aside, use that toothbrush around the seals, brake clean as needed, wipe up the slime, pump a little brake fluid down the system and wipe it on the seals to dilute any of the brake clean. Once it is all perfectly clean lay the caliper on the bench bores are facing up! Now let's pour brake fluid into the caliper bores and fill them to the top, then let's use the lever to pump it down thru the system to purge most of the air while holding the caliper flat bores up so they overflow all the way around, not tilted which would have a fluid void in one area!
Now with fluid literally flowing over the tops of the bores you install the pistons (hollow side up) and shove the first one in a bit which will overflow the second bore, then do the same with the second bore. Next push both pistons the rest of the way in, they can go together or one at a time, you can use the "C" clamp if you wish but what is important here is as you push these pistons in you are flowing fluid back to the reservoir (yes it is making a mess). If there where an air bubble anywhere this will push it right out the top. Once the pistons are seated, and again keep the reservoir full let's pull the lever and pump the pistons part way out again. While doing this watch the fluid in the reservoir to see if any air bubbles come up. Do this until you are totally confident that the system is 100% free of air! If at any time you run the reservoir dry remove the pistons and start over! Now if you have two good heavy duty "C" clamps you can clamp the pistons in a.nd caliper to the bench at the same time, now go pull on the brake while watching the 'C" clamps. If you did it right your lever will still have some movement but as you watch the C clamps they will be flexing by 1/65th of the same amount!
Now let's wipe up the mess at the caliper, rinse with brake clean, tooth brush as needed, and then let's put the brake lining back in place. Now, do not ignore this! I want you to find some sort of spacer about I to 2mm thicker than your rotor. My KTM's rotor is about 4mm thick and I am using a 1/4" (6mm) thick spacer, plywood would be fine, I have a square chisel that I use, put this between the pads, be very carefiil not to run the reservoir dry here, we are going to use the lever to pump the pistons out until they grip the spacer. The object of picking a spacer just slightly thicker than the rotor is to set the pistons very slightly out from their operating position! Once we have set the piston location set, just leave the spacer in place, next fill the reservoir right to the top but try not to get fluid into the screw holes (you can break the casting when putting the screws in if the holes are full), now let's put the cap on loosely. That diaphragm will be displacing fluid so before we push it down let's start the screws that retain the cap to keep the holes from filling up. Then push the cap down allowing excess fluid to slop all over. What we have done here is sealed up the assembly with zero air! When you put the assembly back on the bike, drop that spacer out as you slide the caliper in place, button everything up and then you stroke the lever to bring the pistons out that I or 2mm difference from rotor thickness the level of th.e reservoir goes down very slightly and this is accommodated in the fluid volume changes in the reservoir by the rubber bellows under the cap. We need that small space above the bellows is we need to leave room for expansions of the fluid with heat and now have a 100% air free system!
Draggy! Front brake is dragging? This can be mechanical or hydraulic. If mechanical it is something like a bent rotor, a wheel spacer in the wrong place so the rotor is not centered into the caliper. If something like that you should be able to see the rotor out of center in the caliper and need to find out what is out of place and fix it!
If it is caused by a hydraulic problem the friction will generate heat which will cause the fluid to expand, pressure will increase and lead to the front wheel locking up followed by the never popular face plant! To determine the problem we need to work thru a process of eliminations! So let's block the bike up so the front tire is off the ground:
STEP 1: Can you rotate the wheel by hand?
If so is the drag steady, if "hard, then easy, then hard" the rotor is bent.
If friction is steady it would appear that the rotor is OK?

STEP 2: Apply & release the front brake, does the wheel turn free?

YES: Go ride
NO; Go to STEP 3

STEP 3: Confirm that there is free play in the rod between the brake lever and the master cylinder.
NO; Adjust rods so it has free play THIS MUST HAVE FREEPLAY AT THE ROD, NOT JUST AT THE LEVER! Remember what I said about a fluid port that must be open from the MC bore to the reservoir!
YES; if yes it has free play go to STEP 4.

STEP 4: Disconnect the brake hose from the master cylinder, does the wheel turn free? YES the problem is in the master cylinder, fix* (see note below) or replace NO; Go to STEP 5.

STEP 5: Disconnect the brake hose at the bottom, does that release it?
YES: If yes the problem is in the hose, pinched, kinked or coming apart inside to create a restricted point such that high pressure difference (fingers on lever have about a 5 to one ratio) will force fluid past a restricted point in the hose but the when the lever is released the pressure upstream of the restricted point is released yet a low "pressure difference" continues due to the hose obstruction. This is a high suspect area as much external abuse as these hoses take on a dirt bike!
NO: Go to STEP 6

STEP 6: Is the rotor in the middle of the caliper?
NO Loosen the axle pinch bolts, get a wrench that will turn the axle, hold the steering firmly against the steering stop and rotate the axel while watching the front of the tire 90 degrees from the fork angle, if it wobbles the axle is bent,

STEP 7: The caliper has hydraulic piston(s) on one side only and to apply pressure or release the caliper must slide on pins. Is its ability to slide "bottomed out? If so suspect brake pads are so worn the caliper is out of travel, a bent caliper mount or something wrong in the wheel spacing so the rotor is not centered in the caliper.

STEP 8: Unbolt and remove caliper, does the wheel now turn free?
NO: The problem is in the wheel bearing area rather than brake.
If after all of the above are eliminated if the pistons are not able to retract it has to be internal, probably grunge& corrosion inside the caliper not allowing the pistons to retract. This is suspect if the bike is a few years old and has not had annual fluid changes.
Just a note about brake fluid, brake fluid differs from its hydraulic oil cousin in that it is designed to survive high heat. The stuff that they put in the fluid to make it cope with the heat causes the fluid to become hydroscopic, what that means is it absorbs water. A high performance or "Racing" fluid has more of that "stuff", thus is more hydroscopic. So when they say this is
"Racing" brake fluid, that is better at temps we cannot achieve and more problematic otherwise. Thus "generic" is my choice, it is designed for temps a dirt bike will never see and the more hydroscopic the fluid is the more corrosion you are going to have. A very important part of vehicle maintenance that most ignore is generic brake fluid should be flushed out and replace annually, "Racing" brake fluid much more often! A motorcycle road racer will change his fluid every race and the fast guys, they change it every time in the pits as it has been heat cycled! We off road guys have the opposite problem, water; dirt & corrosion bring an end to the life of most dirt bikes so just because your adrenaline is "up" when your riding is no reason to get "Racing" brake fluid. My preference is to avoid it.
Now when we have it all back together, we have texture on our rotors, the first couple of stops will not be too impressive, best deal is get out in the open such as a road, get some speed up and stop firmly several times, this will get the parts seated in to each other.
*The master cylinder has a simple piston sliding in a bore. The bore has two little holes or ports from the bore up to the reservoir, one small and the other smaller. When the lever is out the piston is back so both of those holes or ports are open from the reservoir to the bore. This is critical so if the brakes heat up, the fluid expands some small amount of fluid from the brake lines needs to move up to the reservoir or the brake will apply itself when hot. Additionally there always needs to be fluid in front of the piston when we apply the brake. When we pull the lever the piston moves and first it closes bigger hole, then with just a bit more movement it covers the smaller hole.
One note for the KTM guys, about installing the system back onto the bike. The clamp that goes around the handle bar has a little arrow like logo on it. What that logo is trying to tell us is that this clamp is asymmetrical. A clamp that is symmetrical you would snug down so that the clamp has equal gap at each side, an asymmetrical clamp is installed so that one bolt, the one that the arrow point to is tightened closing the gap between the MC and the clamp, then the other bolts is snugged up to the desirable tension to clamp on the bar.
 
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