hello, finally i register this thing after almost a year working on it. i go to take it for a ride... as im pushing it out of the garage the front brake starts sticking intermittently. i figure its just the new pads wearing to the disc so i take it for a loop around the block to see if it gets any better... it starts smoking, smells of burning brakes and rotor is extremely hot. when i got the bike i rebuilt the caliper with a kit, replaced the pads, had the rotor resurfaced and changed the fluid. it worked ok for a loop around the block a week ago and was not nearly this bad, so i started bleeding the brakes. sometimes i can get it to not stick when i bleed it but if i take it more than 1/10 a mile it starts sticking again. so i rebuilt the master cylinder because at this point its the only thing i have not cleaned and it still will not go away. its not as bad as this morning when i didnt touch it but its by no means ridable. normally id just get a new caliper lines and master cylinder but this stupid bike is so damn hard (or expensive) to find parts for. please help im stumped on this one, the only possible thing i can think of is the rotor being warped slightly, but when i got it resurfaced wouldnt that fix that?
If you remove the rotor and lay it on a sheet of glass, any warpage should be evident. Did you measure the thickness of the rotor after turning to see if it's still in spec? Like you, I'm wondering if the brake line is the problem. When you rebuilt the calipers, did you clean the pins the pads move on and put a light coating of silicone base grease on them?
the rotor is 4.5mm after the turning (spec is 4mm). i took it to a machine shop when my dad needed some other stuff machined, the guy seemed like he knew what he was doing and it came out looking near new. i completely disassembled and cleaned the master cylinder today after trying bleeding the brakes multiple times (as it was the only thing i had not cleaned up to this point). i cleaned all the braking parts on a wire brush wheel (motor with wheel attachment) including the pistons which had some corrosion (very light pitting on them after cleaning). i greased the caliper pins with brake grease and put the boots on. everything done according to the manual. i even just tried loosening the caliper bolts and squeezing the lever to align the caliper then tightening everything up (had this problem on my 250 before and that fixed it) but the problem persists.
what im thinking at this point... it says 1/8" sae on the line; i cant find any new direct replacements. the part number for it is 45126-MM2-671. so how would i go about replacing the line? the connectors look ok but they look crimped onto the line somehow and i dont know i could get them off without damaging them, let alone get them onto a new line. how should i go about this? thank for the speedy responses!
https://www.ebay.com/itm/115cm-45-M...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
i ended up ordering this. i got a measuring tape for tailoring and ran it along the brake line, taping it in multiple sections. it was about 43" but i ordered a 45" line to account for any human error, better slightly longer than shorter right? i also measured the inside of the eyelet for the bango bolt with my precision caliper and it was just about 10mm (i couldnt get it to fit into the widest point but it was reading like 9.9-9.95mm so ill assume thats a 10mm). so i ordered this "universal" stainless brake line with m10 banjo fittings. lets hope this ebay special "universal" part is actually what it claims to be. ill update when its here.
What you have to be concerned about is how much angle/bend there is on the fittings, and if the ends are in the same plane or offset. That line may be long enough to accomodate any "twist" in the line
the angle on the fittings looks about the same as the one currently on the bike. thats a good point about the ends being plane or offset, why i ordered a little extra. thanks for the help! ill update when its here if its fixed.
I had a similar issue when I fully rebuilt my brake system and had actually replaced the front rotor. I checked the crap out of everything, but then replaced the pad spring with another I had and it seemed to solve.
I built my own SS brake cable with bango ends and line from Revival Cycles
so i replaced the line today... nothing, still sticking :frown2: on the bright side the line seems to work fine so at least that has been eliminated. i ordered a pad spring the same day as the line so that should be here soon. i really hope that guy didnt screw up my rotor resurfacing it
This same symptom happened on my 1985 250 Rebel. Turns out in my case the tiny pin sized hole in bottom of master cylinder was slightly clogged. That prevented all the fluid from returning out of caliper when brake lever was released. Like the OP i checked everything. Did not notice it was plugged with old fluid gum.
Some piston retraction is accomplished by deforming the square cut seal..
bottom of caliper seal groove is typically machined at a slight angle aiding the seal to twist slightly while piston is pushed out by the brake fluid. The deformed seal helps pull the piston back when the pressure is released, allowing pads to move away from the rotor more easily.
piston pitting is caused by water corroding them... Brake fluid is hydrophobic (attracts water out of air)..
Water being heaver than oil (brake fluid) collects over decades at lowest point..
bleeder is at top of caliper, No one ever removes caliper to turn upside down when they flush with new fluid..
that water just sits at the bottom of caliper corroding away till someone pops out the caliper pistons...
So I replaced the rotor, pistons, and pad spring and now we're sticking all over. Mind you at this point I've also rebuilt the caliper with a kit, cleaned and inspected the master cylinder (yes I cleaned both holes completely) and replaced the brake line. at first it seemed ok, the pads were only lightly grazing the rotor, no audible noise, no noticeable drag when pushing the bike. So I decided (after taking it for a shorter test ride the night prior) to take it to the local deli about 3 miles away. The ride up seemed ok, the brake lever did progressively get harder though. When i got there I went in, grabbed a drink, came out to leave and the bike started sticking, I could feel it depressing the forks. I went over a speed hump, and BOOM the forks slam down, the front brake had completely locked. (it even left a skid on the yellow speed hump :surprise Mind you this is in the middle of a parking lot exit, lucky there was no one behind me. I managed the move the bike out of the way by just powering through with the engine until i was to safety, and cracked the bleeder with the provided tool kit (thank God this bike has one) and rode home without touching the front brake. That downhill ride home was the ride of my life (literally). So I got home, ordered a master cylinder rebuild kit; because at this point its the only part I haven't rebuilt. I can't ride my 250 because I was waiting for parts, so I decided to take its known working master cylinder plunger and give it a try. The lever feel improved a little, but it would seem that when the braking system gets hot, the parts are expanding or something and lessening the tolerances causing more brake drag than when the system is cool. I found this video, where a guy bench tests a caliper. He puts a used pad in the pad spring, uses compressed air to shoot the pistons to the pad, and shows the pistons visibly retracting into the caliper. He said, like SoakedKarma the square seals are deforming when fluid is pushed through and causing the retraction when pressure is released. He also stated that corrosion under the seals can cause extra pressure to the pistons, causing them to not retract correctly. So I removed my seals, got the 0000 steel wool and polished those suckers till they shined. But i cant for the life of me get my pistons to retract any visible amount, let alone as much as shown in the video. But I replaced the seals and pistons??? The pistons isn't too difficult to depress into the caliper, I can do it with my thumbs but it doesn't want to move back out in on its own. What could be causing this at this point as I have replaced all the parts to wear? This is the most finicky brake I've ever dealt with :nonono:
Still a good idea to double-check that almost microscopic tiny hole in bottom of the master cylinder. I missed it when i completely rebuilt and cleaned the master cylinder and caliper and brake line. That tiny port is almost invisible. Brake cleaner did not get it cleared out, i ended up using tiny needle and wire strand and compressed air. If it is not fully clear the caliper pistons will remain in brake on position even when the brake lever is released. It visually looked open to me when examined but found internally it was not. Bought the Rebel new back in 1985 and that brake stuck problem is the first time the cycle completely stumped me for a period of several days. lol
The only other thing I can think of is a Blocked Pressure Relief/Compensating/Vent Port
can you see the piston rubber seal retract past the relief port as you release the brake handle?..
Does a small squirt of brake fluid come out of that port as brake applied?..
Wondering if Master Cylinder piston isn't fully retracting
i think you might be right, i watched some youtube and it would appear a little geyser of bubbles/fluid is supposed to come out of that small second hole but its not on mine. what should i use to clean this though? ive already tried my carb passage tool, the smallest one is too big. i tried broom bristles (too big) and wire just seems to bend out of the way before going in (even taped to a screw driver with about 1" exposed). anyone got suggestions? much appreciated
i already took it off and tried that before, but apparently it doesnt work as it didnt fix my problem. i think something needs to get shoved in there to clean out the gunk. i also just tried the smallest sewing needle my wife has and its still just a hair too big and i think thats the smallest size they come in. maybe a special kind of wire?
never would have thought of guitar strings. plunger is seating correctly, circlip is acting as a stopper for it. i just cleaned it with some gunk parts cleaner and compressed air. i can see the compensating hole sucking the cleaner down so i believe it is functioning correctly. the brake isnt sticking all that much anymore, a light drag, i can get about 1-1.5 turns out of it (spinning it as hard as i can and letting go) which is better than the half turn last night. i took it for a little ride on my road (.9miles long private road) just up and down a few times, stopping home jacking the front wheel and the stickyness hasnt changed (like it did last time with more riding). that rotor is HOT though (i was brake checking myself which could cause that) but i dont wanna warp a basically new rotor. would yall say its safe for a slightly longer test ride or should i check out the music store to make certain. im not seeing any bubbles coming out of the holes (either) but the brake appears to be performing correctly. appreciate all the help!
yep, when i initially cleaned the caliper i took out the slide pins, polished em up on my motor with wire wheel, and regreased with brake grease and replaced the boots. buttery smooth now. i think at this point the slight sticking may just be the new pads need to wear, but i thought that last time. should i go to the music store and get the strings to make sure the master cylinder is clean? the compensating hole is sucking down the cleaner when i cleaned it but no bubbles when i push the lever
wouldn't expect bubbles if system fully bled..
without closing off outlet you won't build pressure in master that would cause fluid to squirt out relief.
working the brake lever slightly you should be able to see the seal pass back and forth below the relief hole.
i decided to play it safe and go to the music store. the nice lady even gave me a whole string... for FREE. :grin2: it ran through the passage no problem. it still seems to be sticking as much as before, but im good with the peace of mind knowing that hole is clear. i can get 1-2 rotations spinning the wheel as hard as i can and taking it for a little 2 mile test ride didnt change that. the rotor was cool when i pulled over to check it (i didnt use the front brake as i wanted to check this). do yall think its safe for a longer test ride?
all you can do is ride carefully and test..
in a safe place see if you can get brake to lock up solid and not release, if initial test ride is trouble free.
Glad to hear music store worked out, handy little bugger to have around..
so i didnt have time for a little test ride today, however after those initial rides the rotor did build up some grayish smudge on the rotor (likely pad material transferred to rotor from constant rubbing). i got out the 600 and 1000 grit sandpaper, sanded it lightly all over until the color lightened, cleaning the sections i sanded with brake clean and air before reintroducing them to the pads by spinning wheel. it defiantly spins with much less restriction now. i pushed it up and down my driveway applying the brake here and there (to make sure the pistons were at their seating point) and it seems to be pretty good now. could this have been a possible cause of sticking? ill take er for a ride tomorrow and report back.
I'd expect some pad dust as new pads seat into new rotor..
smudging not so much unless there was a spot or two of brake fluid that had dripped on the disk.
even wiped up a light film of oil would remain and could smear with a little brake dust..
keeping fingers crossed the problem has remedied itself.
Ok, sorry I didnt post an update sooner, been busy work family etc. This sat i put some miles on er, first a short 2 mile test ride, then to a deli about 3 miles away and back, then for about a 10 mile ride. It did good, a little backfiring, I think the air/fuel needs to be adjusted a little out I think its running lean once warmed up. The braking performance seemed pretty good. on the first two rides I didnt use the front brake (except a little when coming to complete stops) and the rotor stayed cool the whole ride (I periodically stopped checking the rotor for excessive heat) and it only got warm like some pizza thats been out for 20 minutes (seems good to me). The third ride I used the brakes in conjunction as I usually would and the rotor got as hot as I would imagine it should (I've never tried to touch a brake rotor after use, but it wasn't scorching hot, smelly, or smoking). Once parked however, it did develop a sort of screech in some spots when the bike is pushed slowly. At first it was LOUD it startled me; I took the pads out and applied some dampening paste and it got much quieter but did not go away. This was in between the ride to the deli and the 10 mile ride, and the braking performance did not change and the rotor continued to stay as cool as it should. Is this something I should be concerned about or is it just because Ive got a basically new rotor with basically new pads and it needs to break in a bit? The sound is alarming, but I've heard a little screeching can be normal with new pads. Also it does not make the noise when I'm riding, even at relatively low speeds, it only happens when I push the bike FORWARDS with it off at low speeds.
It's normal for the pads to not retract enough to not touch the rotor slightly. What you are probably hearing is the light contact of the pads on the rotor.
yeah, there is some resistance when i spin the wheel with it in the air, I can get 1-2 complete rotations when i spin the wheel hard. I dont think its anything to be concerned about at this point, but I will continue to monitor it.
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