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Author Topic: Help! Piston stuck in the rear brake master cylinder 76 CB750F  (Read 3306 times)

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Offline BeSeeingYou

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Help! Piston stuck in the rear brake master cylinder 76 CB750F
« on: February 25, 2009, 09:45:50 PM »
Well I got the rear caliper and MC off today and found the piston is stuck up inside the MC.  Any smart ideas on how to get this out?
« Last Edit: February 25, 2009, 11:12:51 PM by srust58 »
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Help! Piston stuck in the rear brake MC 76 CB750F
« Reply #1 on: February 25, 2009, 10:21:13 PM »
As always the most recommended way is to push the piston out using a grease gun. 
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Offline Gordon

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Re: Help! Piston stuck in the rear brake MC 76 CB750F
« Reply #2 on: February 25, 2009, 10:35:11 PM »
I don't think that method works for the master cylinder.

If the piston is truly stuck inside the MC, it may be time for a new MC. :-\
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Offline BeSeeingYou

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Re: Help! Piston stuck in the rear brake MC 76 CB750F
« Reply #3 on: February 25, 2009, 11:07:12 PM »
It looks like it is two pieces, the piston and the secondary cup.  The cup is on the end of the piston and is what I see pushed up inside.
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Help! Piston stuck in the rear brake MC 76 CB750F
« Reply #4 on: February 26, 2009, 06:26:12 PM »
Quote from: Gordon on February 25, 2009, 10:35:11 PM
I don't think that method works for the master cylinder.

If the piston is truly stuck inside the MC, it may be time for a new MC. :-\

Oh, never said I could read. Perhaps we need to develop a grease gun method on the master cylinder  ;)
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As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline BeSeeingYou

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Re: Help! Piston stuck in the rear brake master cylinder 76 CB750F
« Reply #5 on: February 26, 2009, 11:19:38 PM »
Got it apart.  I heated it up with a heat gun to where it was just a bit to hot to hold and then filled the bore with Deep Creep from the reservoir inlet.  Squirted some in the outlet hole and soaked the cup end too.   After a few minutes I was able to push the cup about 1/4 inch further in to depress the spring a bit more.  It took a fair bit of pressure. Nothing was happening so I pushed it in a little further.  Nothing , so I decided to go to bed and as I put it down it popped apart and the piston just about smacked me in the face.
« Last Edit: February 27, 2009, 11:36:24 AM by srust58 »
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