Moto Morini 500 - sticking brakes

[plc]

Hi All,

A mate of mine has a Moto Morini 500 and he has a problem with his front disc brakes.  The brakes apply fine but they don't release properly.  He has changed fluid, changed seals, checked the callipers and pistons.  He even smoothed out the calliper where the pad had worn a detente that may have cause it to stick on.  The bike has Grimeca brakes.

Has anyone had a similar problem with these brakes or this bike?  If so what did you do to fix it?  He is getting very frustrated.

All the best,
Paul

[Justin B.]

I would have originally thought it to be a caliper issue, or the vent hole in the master cylinder being clogged.  Something else that could cause this would be a rubber hose that is deteriorating on the inside making it act almost like a check-valve...

[nhmaf]

+1 to what Justin said, and, if you are CERTAIN that the calipers and pistons don't have any rough/corroded spots on them as the pistons travel outward onto the disks, I would really look closely at a clogged passageway in the master cylinder - the hydraulic pressure has to be allowed to bleed back - these passages are often very tiny.
Does the brake lever go slack when the brakes are stuck on ? (indicates that the piston in the M/C isn't returning all the way)

[steve hawkins]

My brother just had a similar issue with  Honda 400/4.  His front brake would never release.

It turned out to be the pattern brake pads.  They were far too thick.  Caliper never came into it.

Although we had a great time stripping and rebuild it again and again.

Still we know its good to go now!

[Semper Gumby]

I will be dawggoned.  I had the same problem with some EBC pads on CB400F.  I had to use the Dremel on the metal part of the pad so it would pull back properly from the rotor.

Otherwise I would have guessed the caliper piston has some crud behind it. (The first place I looked).

Good luck.