I think the problem is in the cap not being vented to let the rubber push down right.Because if I try to bleed mine with the cap on I cant get the air out but if I bleed it withthe cap and rubber off it bleeds right out. This could also be effected when the pads wear and the fluid doesnt compensate for the piston movement.

 

Excellent point ftwflh. That might explain why some riders brakes slowly go bad over a long period of time. Now what about the guys that lose their brakes after the first ride. I noticed on my cap, that the rubber at the top of the cap does not seal the cap to the rubber bellows, but the rubber bellows is sealed to the reservoir. It seems that the rubber where it comes in contact with the cap has notches around the circumfence. Seems that air could get behind if it can get past the cap threads. Not sure how reasonable that is though. It seems that a good lesson here is to periodically remove the cap to relieve the vacuum and check the fluid level at the same time. Good observation ftwflh [img]i/expressions/face-icon-small-smile.gif[/img]
Bryce

 

Mine, in general work great, but if I roll it or do lots of wheelies I'll lose my rears. I keep stuff to bleed them in my tool box. Once bled they work well, until the next time they don't.

 

Hey BigBlueScrammy. Seems you are pointing out a key point similar to what Drttrack97 said. Maybe the solution in this case is to keep the reservoir full to the top, so there is no air space above the fluid. Seems if there is little or no air above the fluid, then it can't get in the rear brake line.
Good point BigBlueScrammy.

 

I hadn't ridden my bike in about two months and usually after sitting so long the rear brake would be inoperable. But last time I bled it, I wrapped the reservoir threads woith teflon tape and I STILL have a rear brake. I think the air thing and keeping it topped up might be a viable and simple solution.

 

I had an idea for a solution a while back... what if we made up a bracket to mount and actuate two scrambler rear master cylinders simultaneously? then the lines go back into a Y that goes from 2 lines into 1 and that continues to the rear caliper. seems like it would be more reliable, b/c it would require very little pedal to make big pressure and lock the rear end up. also would definately have more stoping power... just a thought... maybe i'll go fab one up now...

 

Good point scrammy01. It may just be as simple as keeping the reservoir topped off. So you sealed the reservoir cap with teflon tape?
Bryce

LOL ScramblerXLE.. I was hoping we could create a solution that is a bit less drastic. Although that might be a way. [img]i/expressions/face-icon-small-smile.gif[/img]

Come on guys we need more ideas and testing of the ideas presented so we can nail this brake problem. So far we got:
1) Bleed with the cap off to assure no vacuum in the reservoir.
2) Keep the reservoir topped off, no air in the reservoir.
3) Make sure the return spring is strong enough.

 

My scrammy & my tb rear brakes worked all year. this happened only after many bleedings
with the cap & rubber off when bleeding, & keeping it topped off to the max line!

 

Sounds like the key is to top off the reservoir every other ride or so. Scrammy01, did you use the teflon tape on the brake hose fittings, or the screws to hold the reservoir cap on, or both?

 

Good point about bleeding dirtsnow. I notice that my rear brake was a bit lower than my wife's a few months back. When I bled the brakes, I noticed that the air bubbles were so small, you could hardly see them. Seems that maybe we need to look carefully to determine if all the air is out.
Bryce