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Discussion Starter #1
Frustrated! I have a rear brake that, every now and then (im sure by MY fault, but...) drags, overheats, nukes rotor/shoes. Dont know why. Aftermarket rearsets, hose (Galfer), replaced pads, master cylinder, pads, caliper, .... Still, every now and then, nukes rear rotor! Locks almost, have to loosen bleeder to release pressure. Last time- only smoke (evapbrake fluid) out bleeder!. WTF!?!?
 

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Does seem still to be your Rear Master Cylinder , could be leaving enough pressure on to build up heat in the caliper, cant see from the picture , but have you got the brake hose running close to the Exhaust Can
 

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Is the PSR also shielded from heat , and have you tried going back to the Original (just to see if it does the same thing). Any pictures of the set-up .
Have you tried this it has a higher Boiling point for racing
 

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Discussion Starter #7
Yes, not near heat. I actually have switched back to hose and remote reservoir, hoping that will correct. But, still pumping up, and minimal release. Releases enough for me to wiggle rear caliper, but far from "loose". This is on stand. I havent ridden yet since change back to remote reservoir.
 

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Would maybe try that URBF, does seem a problem with heat , if your like me you dont use the rear brake a lot , so heat must be generating from caliper, but is it the brake cylinder not letting the fluid return
 

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Discussion Starter #9
Actually, i do use rear brake alot, but i dont ride it. URBF? I have a new master cylinder coming, I'll try that too. Just tired of replacing parts!
 

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Discussion Starter #11
I switched over to remote reservoir, ill give a try. I also went back to oem rotor and 50% used rear pads (oem), thinner pads than new. All in good condition, removed when upgrading disc and pads.
 

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Is the calliper free To slide on the mounting? And is the rear wheel in straight? Sounds like ceased calliper or binding but you said in post #1 youve changed it already, in fact the whole rear brake appears to have been changed, except how it’s mounted
 

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If the problem started after fitting the rear sets, I’m going with the lever isn’t returning the plunger far enough inside the m/c to hit the relief port.

Do you have the OE rear sets?
 

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Discussion Starter #14
I do. I measured/eyeballed the lever geometry, and its same/similar. Im wondering about the master cylinder location tho. I know im on the very short end of the cycle of plunger movement (screwed in, shortened almost as far as possible).
Where in the "stroke" is the relief valve? Ive never heard of- but does sound like it could be the cause (based on the lack of release).
 

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There is a small “hole” inside the cylinder where the top portion of the piston seal needs to clear on the way down to when the lever is at “rest”. If the return spring is missing from your rear set or the lever Or the adjustment is impeding the return of the piston to “rest”, it keeps its pressure and eventually locks up the caliper.

Had a similar issue back in the day with aGoldwing’s rear brake locking the wheel. We replaced the master cylinder, did the test ride and all showed good. The customer Picked it up and rode off only 1500 feet before it was locked again.

The tech was baffled. Then a friend of mine came in and saw the lever was hitting the giant Kuryakyn aftermarket floor board from underneath (not visible immediately). We slightly notched the floor board and didn’t even notice the lever move, BUT it worked. Never saw that bike again.
 
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