Alright I tore the mc down an honed it alil with 800 and we will see tomorrow ... I hope we r good so I can ride thrusday
Rm 250 rear brake keeps locking up
Started by
jonnyukon
, Jun 24 2012 12:06 PM
26 replies to this topic
Posted 04 July 2012 - 06:11 PM
Well after I honed the mc an cleaned everything again and dropped the brake fluid level to the middle of the full and low mark i rode a few hard laps around the house and used the hell outta the rear brake and no drag or lockup so I think we r good ... When I took the snap ring off the inlet for the reservoir there are two holes one big one on the bottom and one drill hole that barely I mean barely broke threw were there is a very small hole .. Smaller than the tip of my smallest pick... But I made sure they are both clear. An reassembled and it now works!
Posted 05 July 2012 - 04:37 PM
jonnyukon, on 04 July 2012 - 06:11 PM, said:
Well after I honed the mc an cleaned everything again and dropped the brake fluid level to the middle of the full and low mark i rode a few hard laps around the house and used the hell outta the rear brake and no drag or lockup so I think we r good ... When I took the snap ring off the inlet for the reservoir there are two holes one big one on the bottom and one drill hole that barely I mean barely broke threw were there is a very small hole .. Smaller than the tip of my smallest pick... But I made sure they are both clear. An reassembled and it now works!
That small hole is the MC plunger fill hole and it's also an excape for the fluid as it heats up. If that wasn't cleared as the fluid heats up the expanding fluid has no other place to go than to expand the caliper piston into the disk.
If it was mostly blocked before and you did in fact clear it out then you may very well have fixed your problem.
Sounds like you got it!
Posted 08 July 2012 - 10:57 AM
Thanx for everyone's help! Yea before i couldnt even get fluid bled threw it before besides with a vaccum bleeder and this time is was smooth bleeding with out the vaccum tool .Im 99% sure that was it even tho I didn't see and blockage but could've used some glasses to see that small of a hole lol .Now back onto the carb since today is great day for jetting ... If I can't get it dialed in today I'll know there is something up with this carb an I'm moving on to a keihin pwk 38mm quad vent Air Striker and see how it works..
Posted 09 July 2012 - 09:18 AM
That small hole in the MC is the bleed hole. If it clogs your brake won't release, as you know.
Other things that can cause that are collapsed line and messed up caliper pistons.
Easy to diagnose. When the brake system locks, crack the bleeder on the caliper, if the brakes return the caliper is fine. Lock it up again and crack open the banjo fitting holding the line to the MC, if the brake caliper returns, the line and caliper are good. Last, (like you did), clean out the bleed hole in the MC. If brakes still malfunction then rebuild the MC.
Other things that can cause that are collapsed line and messed up caliper pistons.
Easy to diagnose. When the brake system locks, crack the bleeder on the caliper, if the brakes return the caliper is fine. Lock it up again and crack open the banjo fitting holding the line to the MC, if the brake caliper returns, the line and caliper are good. Last, (like you did), clean out the bleed hole in the MC. If brakes still malfunction then rebuild the MC.
