PX125 front brake applies itself...

[daftoldgit]

Afternoon, noob here with a brake problem that's puzzling me.

I have a W-reg PX125 that I've owned from new. It's been on SORN for a couple of years and I recently started preparing it for MOT. Replaced the master cylinder with good s/h fitted with new seals, and replaced the caliper with new. Had the usual difficulties with bleeding, helped by reading posts on here, and the front brake seems OK now; feels reasonably firm but probably needs a bit more bleeding.

However, when the scooter's been standing for a day, the front brake is engaged and I can't move it. Open the bleed nipple and release a tiny dribble of fluid, and the brake releases. It applies and releases without problems and seems perfectly OK. But tomorrow it'll be stuck on again.

Can residual air in the lines cause this? Any suggestions welcome.

[adrian]

I had this problem, and found that the leaver wasn't allowing the piston to fully return. So remove lever and see if it's better. If it is you will need to file some off the leaver where it pushes the piston , so there is a very small gap . Hopefully this will be the answer you need and all will be OK 👍

[daftoldgit]

Thanks, that makes sense, especially as the brake lever is a non-genuine replacement fitted fairly recently (though it seemed to be OK with the old master cylinder -- maybe the new one has a slightly longer piston). When it stops raining here I'll investigate.

[adrian]

I have found that even a genuine leaver needs a little removing to allow the piston to come back fully

[daftoldgit]

That did the trick. I had to take quite a lot off, too, but it's working properly now. Thanks for the pointer.