Have a bit of a problem that showed up before bleeding the systems that I hoped would clear up with fresh fluid but it hasn't. I've looked through the forums I haven't seen a followup that points to the actual cause and how it was resolved.

After riding about 5-6 miles, with a few stops in between, the front brake will apply on it's own and stay clamped until I release the bleeder valve on the right front caliper. Just takes a quick open and close and then it releases and I can continue. Of course my fear is that this will happen more abruptly in the future causing me to do my best improv tuck and roll before hitting the pavement! Doubt I'll be able to stick the landing without a point deduction on form and technique.

I'm trying to determine if I need to think about rebuilding the front caliper itself or the front master cylinder? Anybody have any thoughts or know what's happening and how to fix it? I've seen one post online suggesting that the piston isn't fully retracting causing the pads to rub the rotor and that's causing the caliper to heat up which is causing the fluid to boil thus forcing the piston the engage and not release. This would lead me toward rebuilding the caliper instead of the master cylinder but I'm not sure if this info is right or not.

In the interest of full disclosure the bike is completely stock and I'm the only owner. It has been sitting covered in my garage for 6 years without any love or attention...yes I am a bad parent but I am trying to make it up to her... but after derusting and cleaning the tank and cleaning the carbs and fuel lines this seams to be my last hurdle to overcome before being completely back on the road full time.

Any help or insight is greatly appreciated.

 

I would rebuild it all. Don't take a chance with brake parts.

The caliper releases when you let the pressure out, so the caliper probably isn't the culprit. It's easy, cheap, and good maintenance to rebuild anyway, so do it.
The master cups may have swollen up from sitting. Again, do it anyway.
Replace the brake line. The original rubber hose can collapse internally and act like a one way valve. A stainless steel braided line is a nice upgrade.

 

+1

I suspect the problem is the master cylinder, but a complete system overhaul is in order, especially after 6 years of disuse.

 

definitely rebuild the system. clean the pistons, calipers, replace seals on the M/C


all that's happening is that the brake is getting a little bit of pressure on it, and instead of fluid being able to expand into the MC to the overflow, its bocked - so it expands in the caliper - causing the brakes to be applied.

id think it has to be the M/C along with demon, but you should replace and clean EVERYTHING on your front brake systems. especially since it's sat, it's never been done, and you are having problems.

 

Hey Guys!

Thanks so much for the lightning fast replies! This forum is such a great resource.

Already bled both front and back systems and although they didn't look that bad it was obviously time since the bike has sat for so long. Ordered the front master cylinder rebuild kit and I guess I'll grab the two kits for the calipers as well.

Found colored braided brake lines online for both front and rear for about $145. They're on the wish list but I'm hoping the current lines are alright for the time being but if not then I'll get those too. Believe me, I am on board about how important my brakes are and I'm not going to cut corners here. Is $145 about average? The ones I'm looking at are by CoreMoto.com but Hel seem to be the same price.

Weird thing about bleeding the rear system...pumped the first bit of fluid out but the lever wouldn't pull more fluid in from the reservoir. Had to take a syringe and pump new fluid back in through the rear bleeder to get the lever to build pressure. Read that this isn't uncommon on some bikes but it struck me as strange. Anybody else experience this on the rears?

Any brake pad recommendations? Might not need them but in for a penny...in for a pound right?

Again, thanks so much for all the input and guidance guys...can't thank you enough.

 

if you're trying to save money, and you're not having any problems with the rear, forget doing the rear for right now. i can't remember how much i paid for my lines, but they were much cheaper than that. if you absolutely have to use those lines, run denatured alcohol though them once it's all together to clean them out at least.

as far as pads, it depends on how your ride... i've used organic and HH depending on what the bike was going to be used for. the fighter has HH (for obvious reasons), my gs500, my repsol 954 (didn't ride it hard or all that fast at all), and an xs650 had organic