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Front disc brake locking on

Submitted by keith_parsons on Sun, 28/09/2014
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Commando

Hi

I'm a novice with disc brakes and need some advice.

I've recently bought a 1974 850 commando and have sorted nearly all of it's issues except the front brake. At first it work a bit, but was weak and stiff. So I've had the master cylinder re-sleeved by RGM, fitted new pads and rebuilt the caliper. Now the brake activates ok, but sticks on. If I release the pressure by slackening the bleed nipple it releases ok. Master cylinder problem or caliper??

Submitted by john_holmes on Sun, 28/09/2014

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Its your master cylinder, the plunger is not returning far enough for the seal to clear the second hole and release the pressure, this can be because the conversion has been done incorrectly or the lever is not allowing the plunger to move back far enough. Take your lever off and as you remove it see if the plunger moves outwards, if so file the lever where it bears on the plunger until on fitting it it just touches the plunger. If when you take the lever off the plunger is already fully out send it back to RGM for rectification.

Submitted by keith_parsons on Sun, 28/09/2014

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Previously john_holmes wrote:

Its your master cylinder, the plunger is not returning far enough for the seal to clear the second hole and release the pressure, this can be because the conversion has been done incorrectly or the lever is not allowing the plunger to move back far enough. Take your lever off and as you remove it see if the plunger moves outwards, if so file the lever where it bears on the plunger until on fitting it it just touches the plunger. If when you take the lever off the plunger is already fully out send it back to RGM for rectification.

Brilliant thanks John.

Submitted by barry_carson on Sun, 28/09/2014

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Hi i would also change the flexi hose even though it may look fine on the outside they block internally making a type of one way valve, fluid pumps to caliper but doesnt return. so when you let pressue go at the nipple the caliper returns ok because the fluid cant travel back up flexi hose because its semi blocked holding the caliper on or making it stick slightly . more so when hot.

 


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