caliper troubles

[jmacdbass]

hello all,

I have been having brake problems, one front caliper in particular on my 1979 850g,

when i bought the bike it was having problems staying on (as in it didn't go off) so i brought it to a shop and they took it apart and put it back together getting rid of all the rust spots and making sure everying was free. the one thing it doesn't have is the little rubber boots that go over the pistons

after this i put them back on (i had both cleaned up) and bled the brakes, ok everythings great...

except the next time i went for a ride the same caliper locked up again and my brake lever would get hard at which point i pulled over, unscrewed the bleader cap and bled it a bit and it worked fine again, next time it got hot or sat in the sun it did it again

but its just the one caliper on the front so i have a feeling its a singuler problem and not part of my master cylinder (hopefully)

also my brake light gets stuck on and i am hoping the problems get solved together, any ideas? this happen to any one else?

brake lines all look good and it only happens on the one side

thanks for any words, you guys rock,

jamie

[tomm]

If the brake lever feels hard, it sounds like the bleeder port in the master cylinder is clogged. It is a really, really small hole that allows the fluid to flow back into the reservoir and relieve the pressure on the disks. I had mine plug up on me. Ended up using a one strand of a piece of stranded phone wire to unclog it. Only thing I could find that was small enough to fit. Re-building a master cylinder isn't hard, but you'll need to buy the special tool to remove the circlip that holds everything together. I found the parts I needed at Bike Bandit. And write down how everything fits together when you take it apart. I didn't, and it took several attempts to get it all back right again. One other thing. Keep everything really clean. When you see the size of that bleeder port and realize it's the only thing between you and a locked front wheel . . . Fortunately, when mine locked, I was in the driveway and only doing about 5 mph.

[jmacdbass]

i am going to check into this but when i bleed the right caliper it goes normal again (just turning the valve a little bit on the wheel, and its only the one caliper that has built up preasure), if it was a clogged drain wouldn't it stay hard even if i opened up the bleeder valve?

[tomm]

I'm not familiar with the specifics of the 850 (I have a 78 750), but mine has a single brake line from the master cylinder that feeds both wheel cylinders through a t-fitting. The fact that the brake lever is hard tells me that pressure in the line feeding both cylinders is not being relieved. It it was, one cylinder would be released, one would be locked, and the lever would be soft with the blockage somewhere between the locked cylinder and the t-fitting.

If you want to do a test, try releasing the pressure in the wheel cylinder that isn't locked, next time it happens. I'm guessing that the same thing will happen. The locked cylinder will unlock once the pressure in the whole system is relieved.

[chef1366]

I'm not familiar with the specifics of the 850 (I have a 78 750), but mine has a single brake line from the master cylinder that feeds both wheel cylinders through a t-fitting. The fact that the brake lever is hard tells me that pressure in the line feeding both cylinders is not being relieved. It it was, one cylinder would be released, one would be locked, and the lever would be soft with the blockage somewhere between the locked cylinder and the t-fitting.

If you want to do a test, try releasing the pressure in the wheel cylinder that isn't locked, next time it happens. I'm guessing that the same thing will happen. The locked cylinder will unlock once the pressure in the whole system is relieved.

That is a good idea!:-D

[KEITH KRAUSE]

Grab the caliper and see if you can wiggle it a little side to side. There's supposed to be a little play as the caliper body slides along the caliper axle bolts. How does it compare to the "good" caliper? If no play at just the one suspect caliper, then that's a sign that the piston has pressed against the pad but isn't retracting correctly into its bore when the pressure is released at the lever.
The most common cause of stuck pistons is the piston seal becomes swollen or damaged. If there's corrosion in there, a cleaning may help. Depends on how much corrosion.

[jmacdbass]

master cylinder rebuild

So thanks for the feedback you were totally right, the clymer book says don't bother so I called my local vintage bike place that knows old suzuki's well and they quoted me 80$ for an hour of work and 30-40 for the rebuild kit, is that high?

still not sure how i feel about this particular place but they definately do alot of work and keep expanding

j

[Nessism]

Caliper slides side to side as well, so make sure everything is lubed properly.