Question: Master cylinder bore sizes

[Nooovie]

Hey guys, I've searched the forum, I really did. Does anyone know what the bore sizes were for the front and rear master cylinders on an 81 XS650?

I want to run a different rear master because the stock has strange mounting points and am trying to figure out what other bike to grab it from that would mount up better. So far am considering one from a 2000 GSXR....or a Harley Sportster. I actually prefer the Harley one b/c of the built in reservoir so it looks cleaner. Would it work? Am running the stock single piston calipers front and back. Front master cylinder info would be appreciated too just for having it for future.

Thanks for any info and input really...

 

[littlebill31]

I don't think the '81 came with a stock rear disc. They reverted back to a drum that year.

I think mine is 14mm. It's stamped on the bottom of the m/c. Mikesxs says OEM 13mm replacement m/c.

 

[Nooovie]

Thanks litlebill... mine is kind of a tossed salad of a bunch of years Officially registered as an 83 but I have the disk mags front and back. Now to try and figure out what bore the Harley MCs and the Gixer MCs are

 

[littlebill31]

Not sure about them. There's got to be some tech stuff on the web though. Sorry I don't have a solid answer.