Stuck Master Cylinder Piston - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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Old 05-16-2012, 06:28 AM Thread Starter
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Stuck Master Cylinder Piston

Does anyone now how to get a stuck front-brake master cylinder piston out of the master cylinder?

My bike has sat for a while, and the front brake pistion is stuck/rusted INSIDE the master Cylinder.

I decimated the rubber cap over the piston trying to get it out, and the piston is pretty much flush with the body of the cylinder so I can't get a needle-nose on it to pull it out.

I can't dislodge it through the brake fluid holes (too tiny), and although I haven't tried it yet, I don't believe I'll be able to get enough leverage on it through the brake fluid outlet/banjo bolt hole.

Any Ideas??

John
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Old 05-16-2012, 08:34 AM
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Quote:
Originally Posted by Dr. Frankenstein View Post
the piston is pretty much flush with the body of the cylinder so I can't get a needle-nose on it to pull it out.
Quote:
although I haven't tried it yet, I don't believe I'll be able to get enough leverage on it through the brake fluid outlet/banjo bolt hole.
When this happened to mine, I was able to get enough of a grip on the edge of the piston with a pair of needle nose vice grips then pull and twist.
You may be able to get the leverage to move the piston out just enough if you go in with a flat head screwdriver through the banjo bolt hole. at least I was able to move it a little. I have the old style (square) master cylinder, it may be a little different if you got the round style...

Once you do get the piston out, be sure to thoroughly cleat the cylinder walls out of the gunked up brake fluid that is the likely cause of the sticking. ..and obviously, your gonna want a rebuild kit.

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Old 05-16-2012, 12:09 PM Thread Starter
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Thanks Ndr;

I DO have the square type master cylinder, so I'll give that a shot.

Thanks!

John
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Old 05-16-2012, 01:20 PM
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A buddy of mine had one that was terribly corroded. I ended up boiling it in a pot of water for a while and then got after the plunger with pliers while it was still warm. It was a pain.

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Old 05-16-2012, 11:05 PM
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I had one stuck piston on the brake for my CM450 (it had dual pistons). I clamped the good piston in place (C-clamp), then plugged the brake line hole with a bolt. Next, I attached my grease gun to the bleeder nipple. One or two pumps to fill the caliper with grease, and then the next pump slid the stuck piston right out.

It took hours and hours to clean out all of the grease, but it sure popped the piston out easily. No reason why it shouldn't work on yours.

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Last edited by SnakeMurphy; 05-16-2012 at 11:05 PM. Reason: spelling mistake
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Old 05-17-2012, 02:46 AM
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On my KH500 I have removed stuck pistons by using compressed air. I close off the bleeder valve and blow compressed are where the banjo bolt and fluid would normally go. Watch out they go "POP" when the come unstuck, so dont get your fingers in the way. Best to place a rag over the front of the caliper.

I have not pulled apart a VN750 caliper but If you can get air in there under some pressure it might work.

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Old 05-17-2012, 04:51 AM
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Quote:
Originally Posted by 350ernie2 View Post
On my KH500 I have removed stuck pistons by using compressed air. I close off the bleeder valve and blow compressed are where the banjo bolt and fluid would normally go. Watch out they go "POP" when the come unstuck, so dont get your fingers in the way. Best to place a rag over the front of the caliper.

I have not pulled apart a VN750 caliper but If you can get air in there under some pressure it might work.
Yup. That's what I did when I rebuild the calipers on my VN750, but the OP was talking about the small piston in the master cylinder. Although I suppose that this just may work as well.

......I'd rather wake up in the middle of nowhere then in any city on earth.

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