Rev 3 Rear Brake Problem

[scorpa250]

Help reqd, my son did a real muddy trial the other day on the third lap the rear brake pedal just went down to the bash plate and did not work at all, when home and clean i set about having a look at the brake .Could not see anythink wrong so i put a seal kit in the master cylinder and rebuild .I still cant get a good brake ,i have bleed half a litre of fluid with no success any suggestions ?????

Thanks Paul .

[nigel dabster]

Pads.

[ianwilson]

Bleeding beta rear brakes defies normal logic but the following is the only way i have managed to do it.

1. Remove the rear mudguard.

2. Undo the bolt which holds the rear brake fluid reservoir.

3. Disconnect the rear brake reservoir pipe which goes to the master cylinder.

4. Connect a syringe full( air removed) of brake fluid to the pipe.

5. Attach a length of tubing to the rear brake bleed nipple into a jar or container.

6. Remove the operating rod from the brake pedal that pushes the piston into the master cylinder( remove the retaining pin and clip).

7. Open the rear brake bleed nipple and press fluid through using the syringe. It should flow fairly easily as the circuit is fully open.

8. When clean fluid and no air is coming through close the bleed nipple.

9. Reconnect the operating rod and pin , reconnect the reservoir full of fluid to the pipe feeding the master cylinder and try the brake. It should now work.

If it does not repeat the process again.

Many people claim a quick success with back bleeding by forcing from the bleed nipple back to the reservoir but I have spent ages trying with no success. The method above takes a few minutes and normally works.

If it does not and you are confident that the seals in the master cylinder are in right and the piston moves freely you may want to replace the pistons and seals in the rear brake caliper which is fairly easy and with parts available from Lampkins as a kit for around

[scorpa250]

Thanks Ian, will try your way in the morning, did try with a syring from bleed nipple to reservoir .

[betabonkers]

check the pads cos they dont wear right down to the metal cos the pistons dont seem to come out that far.

hope that makes sense.

[stork955]

Gday, further to all above, make sure there is some small amount of clearance between the actuating rod from the pedal and the caliper piston when it is all fitted up. This is critical!

Cheers,

Stork

[paul w]

as above, but the trick is to have new pads, dont know why but every beta i have owned is like this, once the pads get low the feel at the lever goes. one trick with brake bleeding is to have the pistons out as far as you can, bleed the brake until no air is seen coming down the outlet tube, nip up the bleed nipple and push the pistons right in, this will usually expell any air that is trapped at the lever end.

good luck, i know from bitter experience how frustrating this can be.

paul

[scorpa250]

Right i have bleed from the top to the caliper, from the caliper to the top ( with a syringe) done it the old school way still no joy!!!!! i have split the caliper removed the pistons no sign of any damage they move in and out ok, the pads have about 3/4 mm left on them .if i pump the pedal you get half a pedal they bleed it (old way) the pedal goes again until you pump it again i dont know what to do next . ????????????

Regards Paul .

[paul w]

sounds lke your having fun ! i would try remove , clean and refit the master cylinder rod (just in case). remove the calper so the brake hose is in a staight line vertically up from the mastercylinder and try again.

make sure the pistons are at there fully out position.

when you are happy there is no more air coming out when your bleeding it, carefully push the pistons fully in, watch the resovoir as your doing this, if air comes out repeat the process, not forgetting to pump the pistons out again.

hope this helps

paul

p.s. undo the adjuster on the brake rod just to make sure its getting its full extension.

Edited December 7, 2008 by paul w

[scorpa250]

not sure what you mean .... does the caliper need to be higher than the master cylinder??

how far do the pistons have to out before they pop out ???

Thanks for the help

Paul

[stork955]

Gday -

It can help if the caliper is higher than the master cylinder. Rotate it as well to try and get any trapped air out (air always goes up). Do all this with the cap off the master cylinder reservoir to help the m/cyl prime between pumps. Make sure there is free play between the pushrod from the pedal and the m/cyl piston when it is at rest - this is absolutely vital. Go VERY slowly - take your time - quick pumps just emulsify the fluid and make it harder still. Your pads sound worn past the limit at under 1 mm (unless you meant 3 or 4 mm which is OK), if you are doing this with the caliper off put a bit of wood or something flat between the pads to simulate the disc surface and give the pads something to push against. Dont let the m/cyl run out of fluid or you will have to start again from the beginning.

HTH,

Good Luck,

Cheers,

Stork

[butt mooar]

Bleeding beta rear brakes defies normal logic but the following is the only way i have managed to do it.

1. Remove the rear mudguard.

2. Undo the bolt which holds the rear brake fluid reservoir.

3. Disconnect the rear brake reservoir pipe which goes to the master cylinder.

4. Connect a syringe full( air removed) of brake fluid to the pipe.

5. Attach a length of tubing to the rear brake bleed nipple into a jar or container.

6. Remove the operating rod from the brake pedal that pushes the piston into the master cylinder( remove the retaining pin and clip).

7. Open the rear brake bleed nipple and press fluid through using the syringe. It should flow fairly easily as the circuit is fully open.

8. When clean fluid and no air is coming through close the bleed nipple.

9. Reconnect the operating rod and pin , reconnect the reservoir full of fluid to the pipe feeding the master cylinder and try the brake. It should now work.

If it does not repeat the process again.

Many people claim a quick success with back bleeding by forcing from the bleed nipple back to the reservoir but I have spent ages trying with no success. The method above takes a few minutes and normally works.

If it does not and you are confident that the seals in the master cylinder are in right and the piston moves freely you may want to replace the pistons and seals in the rear brake caliper which is fairly easy and with parts available from Lampkins as a kit for around

[scorpa250]

Thanks for all the replies, its to cold to go out in the garage tonight,will have another go when i have found the will to live again !!!! I have been rebuilding bikes since i was 14yrs old

(27yrs) and i have never come across a problem that i cant sort this is so frustrating .bring back the drum brake !!!I have owned and restored 30+ twinshock trials bikes all the problems they gave me i would swap all those again to sort this out.

[ianwilson]

It just Dawned on me . Are you using a fairly large syringe. It needs a fair bit of force to blast the fluid through.

[ron]

if the pads are more than half gone .. replace them .. seems silly but i have had ajp calipers that are not happy after half of pad is gone but work amazingly good with new pads .. its a much cheaper check than chasing your tail .. if the caliper worked good before then I guarantee it is your issue especially if you have free play at the pedal and your fluid will bleed from the caliper to the expansion tank freely....one mud event in texas one time we went through pads one set per loop .. sandy mud but did happen on all brands..

Edited December 8, 2008 by Ron