Front brake master cylinder problem

[Lug Nut]

02 RSV 16k miles recently dropped/slid down a ditch. Broke right grip and bent/broke front brake lever. Getting everything all fixed up and ready to test drive except front brake. I replaced the lever and now I have no brake pressure or resistance to lever. Calipers don't clamp at all. No leaks. I removed the MC cover and I have pleanty of clean fluid and when I pull the lever I see a tiny bubble come up through the fluid. I am thinking I need a rebuild kit for the MC as a start BUT I thought in would get input from some of you first. The piston depresses into the MC, no fluid leaks, but I assume the rubber could be torn?

 

 

Any thoughts besides rebuild kit for MC?

[Condor]

There,s a strong possibity you have air in your brake line. Try bleeding the brakes before doing anything drastic....

[bongobobny]

Ummm, is the pusher rod (for lack of the proper name) still in place?? I.e. is the lever actually pushing against something?? Could have fallen out when the bike got dumped and old lever got bent/broke...

[MiCarl]

There,s a strong possibity you have air in your brake line. Try bleeding the brakes before doing anything drastic....

 

 

Agreed.

 

Any time a bike goes down there is a good chance of getting air in the brake and clutch lines. The bubbles you are seeing prove it.

[gggGary]

101; bike on side stand the more leaned over the better, bars full left, if needed loosen master cylinder so entire path from calipers to reservoir is uphill. Walk away, every 15 minutes or so (not critical) give a quick squeeze release on the lever, give it an hour or two. Good chance it will self bleed. Any air bubbles slowly work their way up and out as long as the WHOLE path is upward. If that isn't enough you can remove calipers and squeeze pistons back in one side at a time. this will tend to get any air caught in the caliper piston area out and on the way up the lines. Wait replace the caliper then lever squeeze the pistons out to the rotor. This has worked for me many times on MANY motorcycles. My 99 exhibited a sticky brake, first squeeze was kind of jerky hinky brake feel was not reassuring. I pulleded calipers one side at a time, cleaned up everything, pumped pistons out a ways, one at a time, cleaned build up off pistons all around, it can be pretty darned stuck on. lightly wiped with a q tip dipped in brake fluid. and pushed them back in. reinstalled caliper, did other side same way, problem solved, brakes MUCH better.

 

[Lug Nut]

Thaks for the input....I'll try bleeding. Allready bled entire system when I first got the bike back on March....refilled with synthetic DOT 4....installed speedy bleeders....and now have an air compressor powered power brake bleeder. I'll make sure there is no air in the system. If this doesn't do it I'll just get a new master cylinder.

[gggGary]

Pull off and tear down the master cylinder you have nothing to lose and it isn't that hard to do. look carefully for leaks they can be very hard to find the handle hitting something may have put immense pressure on the system and blown something out like an MC seal OR hose or hose/fitting connection or even a caliper seal. Worth a pretty thorough inspection. At least it isn't a snake pit ABS system.

[Lug Nut]

Pull off and tear down the master cylinder you have nothing to lose and it isn't that hard to do. look carefully for leaks they can be very hard to find the handle hitting something may have put immense pressure on the system and blown something out like an MC seal OR hose or hose/fitting connection or even a caliper seal. Worth a pretty thorough inspection. At least it isn't a snake pit ABS system.

 

 

That's kind of what I was originally thinking. Lever hit hard, pushed piston into bore...tore/broke something inside of MC. I'll remove it and break it down when I get a free evening this week. Just a rebuild kit would be nice.

[Lug Nut]

I took off the master cylinder just now...huge Dent in the Piston when the bike fell over and broke the brake lever.....I'm assuming damage to the spring or rubber inside. . New Yamaha rebuild kit ordered.

 

http://i429.photobucket.com/albums/qq14/sbojrab/Mobile%20Uploads/20160912_200811_zpss00hnecu.jpg

Edited September 13, 2016 by Lug Nut