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Potts228

Rear Brake Overheating XR650R

7 posts in this topic

The rear brake on my 650R has been overheating and even though I have been trying to teach myself to stay off of it I still keep overheating it. It never completely goes away but the pedal becomes very spongey and loses it's feel.

I have heard that there is an older Honda Caliper that is larger and will stay cooler but I don;t know anyone that can comfirm this. For now my next step is to drain the fluid and replace it with some Motul 600. Has anyone else had this problem and any suggestions to make it better?

Thanks

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I know xr's only sells a bolt on resovoir that bolts on to the stock one that allows it to hold more fluid. That should solve the problem.

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Your problem is bad fluid. Do a complete fluid change and you'll be OK. Boiled fluid never acts normal once it has cooled down. :mad:

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Bad fluid, and it causes piston in caliper to stick a little which will overheat it in no time. While your at it change the front fluid too.

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The rear brake on my 650R has been overheating and even though I have been trying to teach myself to stay off of it I still keep overheating it. It never completely goes away but the pedal becomes very spongey and loses it's feel.

I have heard that there is an older Honda Caliper that is larger and will stay cooler but I don;t know anyone that can comfirm this. For now my next step is to drain the fluid and replace it with some Motul 600. Has anyone else had this problem and any suggestions to make it better?

Thanks

Something like this happened to one of my friends on his CR500. It has the same brake setup as you 650R. He had a contamination problem. What happened is the tiny hole that the brake fluid uses to get back in the reservior when you let off the brake got clogged. When he hit the brake it engaged like normal. However, when he let off the fluid was stuck and kept the brake on a little bit. For a while he had the symptoms you are describing. Then one day the brake stayed on more and more. Eventually it boiled the fluid and the pressure from the boiling fluid applied force to the brake pads. Not enough to stop the bike, but enough to get very hot. When my friend finally noticed the rotor was glowing red hot in the daytime!!!!

To fix it he had to disassemble the rear master cylinder and clean out the tiny return hole. He tried the drain and replace method a few times, but it didn't fix it. So I'd say try the drain and refill method, but if that doesn't do it, you may have the same problem with crud in the master cylinder.

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The rear brake on my 650R has been overheating and even though I have been trying to teach myself to stay off of it I still keep overheating it. It never completely goes away but the pedal becomes very spongey and loses it's feel.

I have heard that there is an older Honda Caliper that is larger and will stay cooler but I don;t know anyone that can comfirm this. For now my next step is to drain the fluid and replace it with some Motul 600. Has anyone else had this problem and any suggestions to make it better?

Thanks

Before you do all the stuff mentioned above, make sure the brake pedal is not higher than the pegs, you might not notice it with your boot on, but when riding you could be just lighlty touching the brake and that can cause the feel you get, and get used to that feeling if you are using the brake a lot, stopping these pigs aint easy!!! just an easy thing to check before you take the cylinder off :mad:

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This year we were out doing some serious and continuous down hill negotiation at Rowher Flat in Santa Clarita on a 105 degree day. I overheated both brakes and had to eject after turning the Big Red Pig into a Big Red Meteor, streaking for impact on a 60 degree slope with a 120 degree right hander at the bottom! The back went out first and I rode a while using only front brake, which I had been doing for a minute or so. Standing still for about 20 seconds on a little plateau of level ground, telling my buddy how I had just completely lost the BACK brake, the front brake apparently become jealous, had enough of doing all the work, and decided to go on strike as well. So - rolling off in neutral for a bump-start, I had about 2 seconds of free acceleration at the speed of gravity, and a clank with the right foot as the pedal bottomed, and a sick realization as I felt the lever pull nothing.... And had to decide rather quickly how not to end up off a cliff. Picking things up, I sprayed some camelback water on the rear caliper/piston housing, and it was like putting water on a hot iron. Same with the front - they hissed and popped and made some sounds you don't hear unless, I would guess, you forge steel for a living.

They came back to spongy status after a rest, but were never the same.

After a lot of research - (That's what inspired me to register on Thumpertalk) I decided I had enough and went for Galfer Steel Braided lines. Somewhat Expensive. But no problems since. And I've done the same trail 2x more. The final analysis was that in addition to boiling fluid - the extreme heat may have been causing the plastic/rubber brake lines to expand when the brake was actuated. So instead of transmitting brake force to the pistons/calipers, the brake lines were softened and may have been Blowing up like balloons.

There was also evidence of some fliud loss from the master cylinder reservoir when we got home. So who knows if it was just that, or both things that may have factored into the failure.

I didn't want to worry about it ever again (Obviously), so a Buck-fiddy later, steel lines front and back, extra-high temp Brake fluid are on the BRP. No more Big Red Meteor. I Traded Piece of Wallet for Peace of Mind...

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