stuck piston in rear master cylinder

D

davegw

GSX400S Rider
I have got out a rear master cylinder from a pop up that has been sitting around for years,pulled it apart but the piston is stuck in there. Tried blowing out with compressor but doesn't budge.
Any ideas to get it out would be appreciated.
Cheers.
 
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That is clever. I was trying to think how to use some form of hydraulic pressure, but could not think of something easy.
 
Same principle if you've got a stuck piston in your brake calliper. And then a total bastard to clean up afterwards (about a can and a half of degreaser.......)
 
Compressed air - 120psi, and blown ear drums/lost fingers when it breaks fee and shoots across the room.
Grease Gun - up to 6,000psi and a bit of mess to clean up.
 
I think it has been in there for a long time, all dried out and it is the rear master cylinder, so not sure where I could use a grease gun not that I have one. Tried using the air through the banjo bolt opening and through the plastic elbow where the reservoir hose goes to.
 
davegw said:
I think it has been in there for a long time, all dried out and it is the rear master cylinder, so not sure where I could use a grease gun not that I have one. Tried using the air through the banjo bolt opening and through the plastic elbow where the reservoir hose goes to.
Click to expand...

Without seeing it I can think of an issue.
You won’t get much pressure in that chamber as you’ve stated, you have a banjo bolt hole and a plastic elbow. You have to block one and get the pressure in the other and the elbow will be a weak link either way.
Is the banjo bolt hole at the top of the cylinder?
Could you put a drift in there and knock it, or press it out?
 
Boogieman said:
Without seeing it I can think of an issue.
You won’t get much pressure in that chamber as you’ve stated, you have a banjo bolt hole and a plastic elbow. You have to block one and get the pressure in the other and the elbow will be a weak link either way.
Is the banjo bolt hole at the top of the cylinder?
Could you put a drift in there and knock it, or press it out?
Click to expand...


I think I found a pic of one and it doesn’t look like my idea would work.
The next option is to remove the elbow and blank the inlet.
Then you can hook up a front master cylinder and pump it out.
 
If you can rotate the piston and break whatever crud is glueing the piston in, it will make it much easier to push out either hydraulically or pneumatically. I've used the grease gun and air, and if you are using air you do need to use a bit of wood or something to 'arrest' the flying piston.

Of course there is a specific tool to rotate the piston - Brake Piston Removal Locking Pliers. But you might be able to fashion something that achieves the same end.

original.jpeg
 
I'm glad you can get yours to work - I bought a Seeley one of these and it just twists when I try to tighten it and doesn't work. I like yours much bigger and beefier - can I ask where you got it?
 
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Not sure if this will work getting the pictures on, will soon see.
Hopefully that will clear up about the part I am talking about. Have tried wd40 in there,doesn't do shit.
 

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Off the top of my head

Drilling + Extractor at the piston, or

small drilling > middle drilling > large drilling at the piston
 
Similar to rotating, have you tried to dress it in a "little further"? Only a mm or two to break the seal that's holding it.

Can do this with a G-clamp if you don't have a press. Then use air.

If the piston is past the inlet port you'll need to use the Banyo connection end..

If air flows between the two opening, fit a normal bolt as a plug with some plumbers thread tape to the outlet instead of the banyo
 
All good now, thanks to everyone's advice. Finally managed to budge it back after soaking then used some air,then moved it back again and eventually tapping it on the end,it came out. Will clean it up and see what the bore is like.
Thanks again.
 
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