Somebody teach me about master cylinder rebuilding

[HankScorpio]

I have a master cylinder issue in my Sno-Cat. Oddly enough it uses the same general casting as a 60's era chevy pickup. Looks like this:

Normally I wouldn't bother to rebuild one, master cylinders are usually cheap. A 62 chevy pickup has dual 1 1/8" bores, one for clutch, one for brake. A C60 has dual 1 1/4" bores. Mine has one of each which is making finding a new one difficult. I haven't found an OEM version, this was an industrial variant. There is some pitting in the bore and a bit of a ridge. How much honing can these things take before the seals can't take up the difference? Any advice on the honing? I see both 3 stone hones and dingle ball hones available, any preference? I am thinking a 3 stone hone. The Lisle comes as a 240 grit, some others have multiple grits with lousy reviews. There is really nothing to it in theory, a spring, 2 seals, the plunger and a snap ring. I just need to find the right rebuild kit, already found the 1 1/8" side. Any advice would be appreciated.

 

[imiceman44]

I have a master cylinder issue in my Sno-Cat. Oddly enough it uses the same general casting as a 60's era chevy pickup. Looks like this:
View attachment 292034
Normally I wouldn't bother to rebuild one, master cylinders are usually cheap. A 62 chevy pickup has dual 1 1/8" bores, one for clutch, one for brake. A C60 has dual 1 1/4" bores. Mine has one of each which is making finding a new one difficult. I haven't found an OEM version, this was an industrial variant. There is some pitting in the bore and a bit of a ridge. How much honing can these things take before the seals can't take up the difference? Any advice on the honing? I see both 3 stone hones and dingle ball hones available, any preference? I am thinking a 3 stone hone. The Lisle comes as a 240 grit, some others have multiple grits with lousy reviews. There is really nothing to it in theory, a spring, 2 seals, the plunger and a snap ring. I just need to find the right rebuild kit, already found the 1 1/8" side. Any advice would be appreciated.

I used to rebuild my mc before I came to the states.
I used a 240 or 360 grit and just smoothed out any ridges by removing the least amount of material.
I also removed most pitting until it's just a trace.
You probably can remove more and still be fine with the 3 piece honing tool because the seal is usually 1/64th oversized and I am sure you will not remove that much.
You just need to keep it smaller to have tension on the seal.
Pitting isn't as bad as ridges because it could rip the seal

 

[sweetk30]

machine shop over bore and sleeve it if its real bad . then hone it to spec and bam new bore .

 

[diesel4me]

I'd look for a casting number--might be that an automotive application exists for that unit,the manufacturer of the Sno-Cat might have just used one off some truck,rather than having a custom unit made for them..

If the 60's GM truck one would bolt up,and have the same depth on the push rod seat,would the slight difference in bore size amount to a hill of beans,or would it be critical to have it match exactly to the original ?..

The "best" rebuild method for master cylinders (and calipers ) is to have them bored out and a brass or stainless sleeve put in them,as Sweet K30 said..that is the longest lasting option..

That said,I have used the honing stone tool intended for master & wheel cylinders to clean up rusty pitted bores on my old VW's and a '66 Buick master cylinders,and I didn't have any issues with the seals leaking or by-passing fluid--but I may have just been lucky too..