Anybody know why the piston in the master cylinder would be sticking. I took the brake lever off and noted that when I press the piston with my finger it doesn't stick if I push it in perfectly square to the reservoir. If I apply any sideways pressure (as happens when the brake lever is pressing it) it will stick. It does depress to apply the brake but its dangerously jerky - sticks and lets go after appling enough pressure. Not good when riding two up - more than the ego gets bruised !!

So what's up with that??

Dandy D

I'd pull the MC off and check to make sure the bore is in good shape.  If you need to replace the piston/spring ass'y, they come as a set (piston,spring,circlip).  

I don't know if that sort of thing is normal, but it would have me spooked enough to pull off the MC and give it a once-over.

Yes, it shouldn't stick. It may need a good cleaning and rebuild .

Thanks for the advice. I'm a total noob at this. Anywhere on the site that could walk me through the process? Don't want brake fluid all over the bike and want to make sure I put it back together properly. I do have the Clymer manual. I'll have to check that for something helpful too.

Thanks again.
Dandy D

Just pull your pads like normal but give everything else a good scrubbing with a toothbrush and brake cleaner.

Let me know if you end up doing a rebuild on your master cylinder.  I did one just the other week, so I can walk you through it.  It's not that difficult, just time consuming, and a little scary (you don't want to screw up on your brakes).

Well the Clymer manual does show the steps in taking the MC apart - doesn't look too difficult. I don't have a circlip tool though - would needle nose pliers work??  :dunno: If I do tackle this on the weekend will I need to empty all of the brake fluid or just what's in the MC? Can I then just top up the fluid with new?
If I do have a piston ass'y problem, I don't have a replacement. I hope a local shop has one in stock- cause it takes bloody forever to order in parts here. (5 weeks in total for a rear foot peg and I'm still waiting for a F-15 tour shield that I ordered April 30  :x )

Ar5senal, I'll keep your offer to walk me through it in mind for sure - thanks
Dandy

Needle nose pliers won't work, you'll need small circlip pliers for this.  You really only need to drain the brake fluid from the MC: i.e., leave your brake line attached to the caliper, and make sure it's vertical, so the brake fluid doesn't drain out.  However, I would just as soon flush the whole system...it's not that much brake fluid, and it makes me feel better knowing that i have all fresh fluid in there.

When you disassemble the MC, take a look at the bore (use a small flashlight) and as long as it's not scored up, you should be golden.  Be very careful not to bend the circlip when you take it out, since you won't have a replacement.  Clean everything with brake cleaner, and make sure everything's dry (and dirt particle free) before you reassemble.  lube the piston ass'y with brake fluid when you reassemble.  Maybe you could post up pictures of your piston & spring, and someone here could tell you if they look out of whack or not.  Good luck