Front Brake Issue - 600RR.net
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post #1 of 6 (permalink) Old 09-25-2008, 02:23 PM Thread Starter
 
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Front Brake Issue

Ok, full story, be patient. I wrecked in July, 07 CBR600rr landed on right side, broke front brake lever and foot peg off, scuffed the right fairings up pretty good, bent throttle cables. I replaced the levers with ASV's and install went on smooth. I mentioned in another post about the banjo fittings leaking at the lever and I tightened the bolt and no more leaks. Brakes felt and worked great, that is until the other day. Buds n I were riding and five minutes into the ride we take off from a stop sign and it starts to slow as if I was losing fuel, I gassed it and it got slower, my buds swerved to miss me b/c now it was stopped in the middle of the road, as I pulled in the clutch she locked up no moving. As I tried to move out of road I noticed the front tire was locked up. Brake lever was hard as a rock. We bled some pressure of the lower right caliper bleeder and all was fine. We were on way to bike shop so we continued w/ no issues. The mech said he had no clue why it happened especially since it was working now.

I've since talked to others and possible reasons are 1) Trash in the system could have clogged a port in the caliper not allowing fluid to return which caused the fluid to heat up expand and force the brakes to compress. 2) The new levers will sometimes need to be shaved down where they press against the piston in the master. Often the misfit lever applies just a small amount of pressure to the brake. This "drag" will cause enough heat to build up and eventually lock the brake.

I tend to lean towards #1 b/c I've ridden further and harder on the brakes w/ no issues. Solution recommended to #1 was to back bleed the brakes and it should force the trash out the reservoir.

Any Ideas or advice???
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post #2 of 6 (permalink) Old 09-25-2008, 10:31 PM
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My guess, you lever isn't fully releasing the brakes. This does 2 things. 1st heats up the brakes and the fluid, this isn't too much of a problem cause they're made for that.

2nd, (and this is what I guess it would be) with the brakes slightly applied, The piston in the master cylinder never opens enough for fluid to flow from the res. to the lines. 1 problem, as the fluid gets hot, there is no place for it to go, the res. is cut off so it builds pressure in the line.

After some time and your pads wear, you will have to keep pulling the lever forther in to stop. As the pads wear and move in towards the rotors, the caliper will hold more fluid and it no more fluid gets into the system from the res. then you will eventually not be able to stop.

Sorry for over explaining this, I think you need to re-adjust the new levers. If you want to test this idea, Take off a caliper and try to open the pads, if you can't then the res. is closed off. If you can, then dis-regard everything I just said.

Good luck.

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post #3 of 6 (permalink) Old 09-28-2008, 03:52 PM Thread Starter
 
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Originally Posted by dcope17 View Post
I think you need to re-adjust the new levers. If you want to test this idea, Take off a caliper and try to open the pads, if you can't then the res. is closed off. If you can, then dis-regard everything I just said.
Ok, Thanks for explaining this. I did what you suggested and the pads were able to open....now what? Flush out my lines with some new fluids?

I tried a test run before doing this test and after about 5 mins of riding, it did it again, locked up, I bled off the pressure and came home to try to open pads.

Another question....I noticed in the manual, that once you take the brake caliper bolts out, you're supposed to replace them with new ones. Is that right???

Thanks again for your help dcope....cool sig!
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post #4 of 6 (permalink) Old 09-29-2008, 12:43 PM
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The only other thing I can think of is a new master cylinder. Dirt in the lines can cause problems but it has to be very significant. To lock up your brakes taked quite a bit of line pressure. It would take a perfect clog to lock up your brakes and not even bleed off a little pressure. ( I know Jesus is perfect but sorry, this clog isn't )

If everything works right cold and locks up when it gets hot, then heat and the expansion that comes from the heat has to be the problem. The only place that this pressure gets relieved at is the master cyl. when the lever is fully released. So my first thought was that the m/c wasn't releasing all the way from installing a new lever.

The only thing I can think is that the m/c got dammaged from the crash. I don't understand how a small crash that probably just squeezed the lever back to the bar would mess it up to where it works sometimes but I don't know what else it could be.

The calipers are working correctly. they work when they are cold, and after they lock up, you bleed off the pressure and they work correctly again. So they are doing what they are supposed to. Pressure = stop... no pressure = roll

Your lines work, squeese the lever and the bike stops. If it had a weak spot, the brakes would feel spongy, (maybe not even enough to notice but that's what would happen) not lock up for no reason, and they don't leak. So that is good.

Only one thing left. M/C. I wouldn't think heat would travel all the way up the brake fluid to the M/C but I guess it can. Maybe the heated fluid does something to the m/c maybe expands a seal or something. Maybe the res is too full. ( I think it would leak before it held enough pressure to stop the bike, and I don't know if you can fill it to the rim unless you try really hard) The problem is somewhere in the M/C. Racers upgrade to Brembo M/C's and sell their stock ones all the time. Find a stock one on Ebay or even buy a brembo. For just street, stock is fine.

I hope this helps and it wouldn't hurt to clean the lines or bleed them and that is cheaper than to buy a M/C but I think the M/C is the problem. Have fun and I hope you get riding soon.

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post #5 of 6 (permalink) Old 10-01-2008, 11:21 PM Thread Starter
 
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Ok, I finally called the manufacturer of the lever, ASV, and they suggested loosening the bolt that holds the lever to the master cylinder. They said it only needs to be tightened to like 5ft/lbs torque. Well, it took way more then that to loosen it. They said that would cause my problem and since I've loosened it, no problems at all. It stops when it's posed to and rolls when I gas it! Apparently the lever was not fully releasing and thus causing the overheating issue and the fluid to expand.

Thanks for all the help and advice, I really appreciate it!!!
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post #6 of 6 (permalink) Old 10-03-2008, 04:58 PM
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Have fun riding. Nice profile Pic by the way.

Ride hard today, Ride harder tomorrow,!
Walk close to Christ today, Walk closer tomorrow

How to fix headlights... Dreamzboy's excellent write-up
https://www.600rr.net/vb/showthread.php?t=138034
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