Another rear master cylinder question! PLEASE HELP

[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?

[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.

[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]

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:







Soaked it in WD-40.



This is after 3 hours:





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:





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]

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

[retrex]

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.

[Jeff Bennetts]

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



jb

[EMS]

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