270 Rear Brake

[yoyo]

I've been suffering with occaisionally losing the rear brake on my 270 rev3 since I've had it.

I've got recent pads in it. I've stripped the caliper and lubed and cleaned it and bled some new fluid through it. However the problem still persists.

What happens is that after a short while the pedal travels all the way down and touches the bash plate and is not stopping the rear wheel from turning.

I took a couple of pics of a 125 rear brake set up to see if I could set mine up properly with regard to the position of the lever stop (adjustable bolt by the swinging arm pivot) and also the actuating arm/rod which goes to the master cylinder. My initial thoughts were that the piston in the M/C was being pushed up to far inside the cylinder and fluid was by-passing it. I adjusted it back so the actuating arm/rod wasn't so far up inside the cylinder.

It was fine for a short while but now I'm back to square one again. I've got a couple of trials coming up in the next 4 weeks and I really don't want to be in the position of riding with only the front brake after a couple of sections!

any idea's?

A mate suggested a new M/C but the bike is an '06 and hasn't done a great deal of work really so I can't see how the components in it could be worn already.

All tips and hints gratefully recieved....

ta

Shaun.

[jse]

I took a couple of pics of a 125 rear brake set up to see if I could set mine up properly with regard to the position of the lever stop (adjustable bolt by the swinging arm pivot) and also the actuating arm/rod which goes to the master cylinder. My initial thoughts were that the piston in the M/C was being pushed up to far inside the cylinder and fluid was by-passing it. I adjusted it back so the actuating arm/rod wasn't so far up inside the cylinder.

A mate suggested a new M/C but the bike is an '06 and hasn't done a great deal of work really so I can't see how the components in it could be worn already.

Shaun.

Shaun,

I'd first set the lever stop to where it's comfortable for you and then check the plunger rod on the back of the lever to make sure that it has a little "slack" before it starts to press on the piston inside the master cylinder, otherwise adjust it back down till it does. You need the piston to return completely back down to it's stop at the circlip. Each bike is different, so the settings for the 125 may not work on your bike.

I doubt you need a new M/C, but you may need a rebuild kit if the seal has worn to the point where it is inconsistant in operation. Sometimes a worn seal will not "seal" until it is part way down the bore as the first third of the bore gets the most use and only a few thousands of taper in the bore will cause problems.

I'd check the lever adjustment first and then maybe opt for a rebuild kit. I'd also try to keep the line ziptyed up when taking off the M/C (or try to replace parts with the M/C held up) so it doesn't drain down and you'll find bleeding the rear brake a lot easier. You can often bleed off any air from the system by pressing on the M/C piston with a Phillips screwdriver after assembly.

Jon

[micm]

Two new Betas have the same problem in my area - South of England. One is 4 stroke one a 270. A rear cylinder was replaced on one after 2 trials. It has been suggested the cylinder casting flexes slightly causing the problem. The all make bike test in YOU HAVE USED WORDS OR A PHRASE WHICH ARE NOT PERMITTED ON THIS WEBSITE. PLEASE DELETE YOUR POST/TOPIC. DO NOT TRY TO CIRCUMVENT THE FILTERS IN PLACE ON THIS WEBSITE recently highlighted Beta brakes as less than ideal. A new 250 2 stroke I tried during a trial at Christmas had very poor brakes - they ruined the bike for me.

[ptradam]

I had a similar problem with my 05. Are you sure the plunger inside the master cylinder is traveling all the way back out after you let off the brake? The master cylinder on Betas are right above the chain and get slathered with all of the chain lube, mud, and water that slings off of the chain. Remove the master cylinder from the bike and give it a good cleaning inside and out. Take it right apart and make sure the o ring is good and everything. Lube it up good with WD 40 or something so it doesn't have any drag. Hope this helps.

[anotherfive]

Before stripping completely try this. Remove cylinder from frame. With a flat blade screwdriver press on piston and at same time try to rotate the piston say 1/4 turn. Nowsee if it will push to brake and return back to circlip stop. This has worked for me in the past.Remove all muck and clean at the same time. New seal kits are cheap but a bit fiddly to get on.I use the pointy end of a pencil to get the seal stretched a bit. Then slide directly onto the piston from the pencil." just a tenner for that thanks!!!"

[Guest iwilson]

Ive seen and suffered this problem on several Betas. Save youreself some time and ring Lampkins for a seal and Piston kit (2 seperate part No.s)for the rear master cylinder. You will need fairly good circlip pliers to strip it down. Reassemble and flush through with a syringe of brake fluid in the pipe removed from the bottom of the rear brake reservoir with the bleed nipple open. The seals break down so you will see lots of grey and black gunge come through the bleed nipple. Close the nipple and check to see if you have a brake.If so refit the pipe onto the reservoir and bleed the last bit of air in the ususl way. I have never successfully bled the brakes without a syringe. It can take a while to get all the air out.

The root cause of the problem is that the piston is soft alloy and over time or if there is too much travel it goes oval and sticks halfway up the casing in the M/C. Ive also seen the brakes bind and overheat from the same cause. turning it is a quick fix but it will stick again !!!!!