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Discussion Starter #1
So after much grunting and impact wrenching i got my caliper apart on my 73' CB750. Pulled the pads out and i cant get the piston or cylinder out. Wont budge, i tried pumping the lever, that dosent do anything. Can i pull it out w/ pliers or will that screw something up? b/c i pulled on it and it didnt move. Looks kinda cruddy around there too. The brake was working fine when i took it off.

The fluid in line/screw wont come off either, i got the other one out w/ the impact wrench but cant use that on this one.

Any suggestions or tips? Every time i take something apart on this bike something gets stuck, everytime, fork bolt was stuck, oil drain was jb welded, trans cover screws are stripped, its driving me crazy. And i want to stab honda in the throat for making all these bolts so soft.

here are some pics





My CB750 Project:
http://www.caferacer.net/forum/topic.asp?TOPIC_ID=4739

Edited by - kawiracer on Oct 09 2007 12:50:50 AM
 

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those things seize up like a motherfucker, don't they?

I had to cut the little pipe above the fitting, and then use a socket while the whole caliper was clamped in a vise. good thing I had a spare brake line.

what a pain in the ass that was. My piston was stuck as well, but I just re-filled the reservoir, and bled the brakes (took a long time) and eventually the piston popped out. took a long time though. watch out for a mess when the piston finally pops out.

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My CB450 project:
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Discussion Starter #3
quote:
those things seize up like a motherfucker, don't they?

I had to cut the little pipe above the fitting, and then use a socket while the whole caliper was clamped in a vise. good thing I had a spare brake line.

what a pain in the ass that was. My piston was stuck as well, but I just re-filled the reservoir, and bled the brakes (took a long time) and eventually the piston popped out. took a long time though. watch out for a mess when the piston finally pops out.

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My CB450 project:
http://www.caferacer.net/forum/topic.asp?TOPIC_ID=2827
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i might have to try the cutting the pipe thing, because it is not moving. the thing is so soft that the edges are long gone and im not gonna be able to use a socket.
 

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you should do a search on the topic, i've seen this discussed a number of times

...connoisseur of slack...
 

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Go to your local parts store & buy PB blaster , its like wd40 but works 3 times better. spray your parts real good let them soak for about 10 min & spray again. After that its Vice grip time get them on there as tight as you can , theres been times Ive actually welded my vice grips to a bolt to get it off & it worked . Good luck man take your time when ya get frustrated just walk away & go have a beer & re group.

see pics of my rebuild here

http://www.myspace.com/whiteboytsbr
 

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I just had the same problem with the caliper piston. I put it in boiling water for a bit, then I grabbed them with a set of robogrips and twisted them as I pulled. My forearms hurt when I was done, but with enough pressure they came out eventually. I also noticed that when after I got them started, long flathead under the lip of the piston could be used to slowly pry them out. Good luck.

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compressed air. be sure to wrap the caliper in something cuz the piston and all the fluid behind it will come out like it was shot out of a rifle. wrap it up in shop rags or something to keep the piston from flying.

the hose bolt is brass. you could try drilling it and then pulling it out. pb blaster is the bomb. shit works wonders. been using it for years.

jc
 

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like joe said, "compressed air." however add heat from a torch to the caliper and not the pad. have an oven mit ready cause it will pop and be very effin' hot!

tex
 

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quote:

don't pry on the piston if you can avoid it.
I was sure to do it gently and only a little bit at a time. Also switching from one side to the other in order to keep it as even as possible.

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quote:
If you can adapt a grease fitting to the bleed hole you can use a grease gun to force it out.

FC
I tried everything with my caliper to get the seized piston out. Boiling water, compressed air, prying, beating, cussing, etc.

this was how I finally got it out, worked like a charm.
 

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Discussion Starter #13
thanks for the advice. ive used penetrating oil on that bolt but its done nothing, ill try the PB blaster.

a couple people have said to use a grease gun on the piston so ill try one more time just using more brake fluid and then ill do that, i dont have a torch to head it with. i would think heat would only make it expand?
 

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yeah, heat will make the caliper expand faster then the piston so it will be more apt to come out. if all the air is out of the line (bleed the brake well) then top off the brake fluid and start squeezing the handle. as it starts to move the piston, you will need to add more brake fluid. it will come out because you said the brake was working fine before you took it off. they are just a pain in the arse.


'72 cb750
'76 cb550
'76 cb750
 

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If you can get enough pressure behind it compressed air always works. It's nice to have a rubber tip for a good seal. However, I don't use the Joe C. method of wrapping a rag around the caliper, I prefer to fire the piston out into the nights sky. I actually did it just the other night on my friends crusty KZ. Good luck and don't put your eye out ;(
 

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Discussion Starter #17
so i got the fill bolt and pipe off. i heated w/ a torch and the thing came right out, cant believe how easy it was.

the cylinder is being stubborn though, i cant even seem to get all the air out of the line, w/ fluid i still cant get it to budge.

My CB750 Project:
http://www.caferacer.net/forum/topic.asp?TOPIC_ID=4739
 

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got an air compressor? if so get a rubber tip for it, then heat the side of the caliper for a minute or two with lp or map gas. then cram the rubber tip down the treaded oil hole and blast it with air. have it pointing down or you will take you eye out.

good luck.

tex
 

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Discussion Starter #19

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I thought it was a good enough idea that I bought one (sorry to snake the auction but he does have more - that wasn't his last one) since the caliper on my 73 has a really nasty piston. so yes a stainless piston is a good idea.

if you didn't have the button it probably didn't make a difference in anything except squealing. I have taken apart enough calipers in my life and about half have them and half don't so.....
 
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