Another rear master cylinder question! PLEASE HELP

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cba
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Another rear master cylinder question! PLEASE HELP

Post by cba »

Okay, I have managed to get the old seals and piston out! Finally after soaking in WD-40 for a couple of days. My problem now is the rebuild kit I bought at Honda is different! The seals and all the hardware seems the same, but the piston is totally different in design and a tad shorter. The illistration in the Honda manual looks like the one in the kit, but the one I blew out of the housing looks like a corkscrew in between the two ends! Does this make any difference?
AM I THERE YET?

rigidmotor
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rear brake kit

Post by rigidmotor »

never heard of corkscrew pistons. unless your housing is after market then your kit should work. just be real carfull in cleaning the walls of the housing. did you get any lub? the shop should have some, the kits i used to put in for H/d's came with a little packet and if all else fails would use seal grease ,also you should get some from your shop. talk to your mech. there if parts guys are dumb as most are when puting things together. this is my view from a guy who tryed to make a living as a mech in kansas and found it don't pay for s--t in this state. now just working on my own and friends.

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real6
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corkscrew piston

Post by real6 »

I found a corkscrew type piston in a Honda M/C that a took apart for parts, and wondered the same thing. I suppose I'd put it together and try it although the length could be an issue.

Octane
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Re: Another rear master cylinder question! PLEASE HELP

Post by Octane »

cba wrote:Okay, I have managed to get the old seals and piston out! Finally after soaking in WD-40 for a couple of days. ....


Don't.

I used to do the same thing. Not anymore.

WD-40 will make the seal expand and make matters worse.



Did a bit of 'research' for another forum I frequent:



Piston seal (for Honda GL1000) in container:

Image





Soaked it in WD-40.



This is after 3 hours:

Image



You can see that it has swollen up and expanded to the point

where it touches the sides of the container







This is after 48 hours:

Image



I' surgest using something else.

After I discovered this

I've used contact cleaner witch worked fast and fine.

(Do note that it is highly flamable)





Regards

Octane

Dave Ditner
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master cylinders

Post by Dave Ditner »

Use alcohol to clean them and brake fluid for an assembly lube. The seals are EPDM and don't tolerate petroleum based fluids.
Davey

9 Xs: 4-79s, 1-80, 1-81 and 3-82s

retrex
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Re: master cylinders

Post by retrex »

Dave Ditner wrote:Use alcohol to clean them and brake fluid for an assembly lube. The seals are EPDM and don't tolerate petroleum based fluids.


What Dave said and if you have brake caliper housings, mounting brackets or rotors caked with dried brake fluid you can use Xylene to desolve the dried fluid and clean them. It dosen't harm the paint on the calipers. Make sure there are no rubber parts on the items you clean. After cleaning with Xylene wash the parts with Simple Green, or equivalent, and rinse with water several times to remove residual Xlylene. Air dry and then rinse some more with Denatured Alcohol before reassembly. Note Xylene is dangerous, use with adequate ventilation.
1982 Honda CBX - Mobile and loving it

1981 GS1100EX - Undergoing rebuild

1981 GS1100EX - Rolling rebuild

Why two GS11s? A man doesn't feel like a man unless he has a big pair.

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Jeff Bennetts
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Post by Jeff Bennetts »

The rear master cylinder internals are different for the 79-80 from the 81-82.



jb

EMS
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Post by EMS »

Late models use the parts as first used in the 1980 CB900 Custom.

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