Disappearing/re-appearing rear brake - stumped. - Kawasaki KLR 650 Forum
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post #1 of 10 Old 09-09-2012, 09:56 PM Thread Starter
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Question Disappearing/re-appearing rear brake - stumped.

Put about 250 miles on my 2009 garage queen today.

She's only got ~4K miles on her and, for the first time, got her dirty and hit some gnarly fire roads in the hills.

I experienced a problem with the rear brakes that I am stumped about: While riding on the fire road, at one point the rear brake was working fine. I remember because I locked up the rear wheel for a sec on a tricky descent.

Just seconds later the brake pedal went completely down as if there was no pressure. I thought for sure a rock had hit the master cyl. I tried pumping the pedal and could not get any pressure back.

My riding buddy was ahead so didn't bother stopping to inspect, just kept on going. Ten minutes later, the rear brake had pressure again. "How freaking odd," I thought to myself.

I caught up with my riding partner and we stopped and looked at the bike. The line was fine, brake fluid level was fine, caliper was fine, pedal was still in place. Other than being dusty, everything looked in order.

This happened three more times while riding off road. Rear brake would disappear, no pressure, then 5-10 minutes later mysteriously start working again.

During the remaining 2 hours home on the twisties and then the slab no more problems. Rear brake works fine sitting in the garage right now. Plenty of pressure.

I am completely flummoxed as to what could be causing this. I've never even had the rear wheel off the bike yet. Any ideas?
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post #2 of 10 Old 09-09-2012, 11:08 PM
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Yeah,
I'm thinking a lot of break bleeding is in order. I was just thinking of getting a brake bleeder thing to make it easy.

By they way Klrdoood, Thanks for helping me pickup my bike when I biffed today..



Welcome to the forum... No go sign up for the Tech day so we can adjust your valves and fix your brakes..
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post #3 of 10 Old 09-10-2012, 02:25 PM
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Sorry, don't have any ideas but i had the exact same phenomenon happen to me with the front brake while coming coming up to a stop sign. It only happened that one time and never happened again for as long as i owned the bike. I was going to bleed the brakes but could not get the philip screws off of the resevoir so i chalked this up the an anomoly and left it at that.
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post #4 of 10 Old 09-10-2012, 03:40 PM
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I bet you boiled the fluid in the rear caliper and that has caused it to have air in the system. A bike with that few miles shouldn't have anything wrong with it's brakes in a mechanical way like damaged master or piston and if it did it wouldn't come back on occassion either.....from what I have found

I recommend a complete drain and ew high quality fluid installed and bleed the daylights out of it.

Willys
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post #5 of 10 Old 09-10-2012, 03:45 PM
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Sorry, another idea, do the pads in the caliper move freely around within their captive locations? OR are they wedged tight in them. If tight your brakes can't release all the way and will drag a bit. Most pads need to be gently filed or carefully ground down where the pressing marks are from when they stamped out the metal the pads are glued to. Once you have a freely moving pad you will find they operate much better..
Secondly.....maybe you were standing on the pegs and accidentally were also hitting the brake causing the caliper to heat up and boiling the fluid???


Just a few more thoughts

Willys
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post #6 of 10 Old 09-10-2012, 10:16 PM Thread Starter
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Guys,

Thanks for the replies.

I did some more research about this and, yes, I'm pretty sure I was boiling the fluid.

Definitely the original crappy brake fluid in there (has a brownish patina to it, haha) and apparently the KLR is notorious for overheating the fluid as the muffler is very close to the reservoir. Not to mention I was thrashing the bike pretty hard.

Will grab the the mityvac and throw some new brake fluid in this weekend.

And definitely hitting that tech day and hope to learn the ins and outs of KLR valve checking and adjustment - thanks for the heads up, Cabrito! (BTW, love that mini-mount rushmore in the background of your pic).
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post #7 of 10 Old 09-11-2012, 07:46 AM
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Just as a heads up......valve must be checked when the engine is stone cold or the readings you get will be incorrect. Metal expands with heat and thus closes the gap on the shims....just saying.

Willys
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post #8 of 10 Old 09-26-2012, 06:43 AM
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This happened to my bike as well on three different occasions while coming down really steep fire roads in the mountains. I took it to the shop after the first time it happened with 3500 miles. Everything checked out fine. The problem was that the fluid got hot and it just needed to cool down. I had never experienced this before on any of my other bikes, but the shop says that this isn't uncommon during those types of riding conditions.
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post #9 of 10 Old 09-26-2012, 08:53 AM
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Would upgrading to steel braided brake lines help with this problem?

I've never had this happen on my Gen1

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post #10 of 10 Old 09-26-2012, 09:25 AM
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Quote:
Originally Posted by Cabrito View Post
Would upgrading to steel braided brake lines help with this problem?

I've never had this happen on my Gen1

IMHO it's usually a technique problem not mechanical. If you ride with your foot over the brake pedal all the time you will cook the fluid especially off road where you may have a tendency to put more pressure on it.

Good technique is having the balls of your feet on the pegs not the arches. You move your feet to brake and shift. If you have to ride with your foot over the brake pedal lower it down so it takes a good stomp to engage.

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