I just went through all of this on my '70 Spit. It started out that the
primary seal in the kit kept splitting when installed. I then purchased
Girling seals (which didn't split) and the cylinder still leaked from the
primary cylinder. Talked with TRF and decided to have it re-sleeved. I sent
the cylinder to Apple (I have no connection) and it was nicely re-sleeved for
around $100.00. Re-assembled cylinder and bench tested it, guess what, yep
still leaked. Pitched large allen wrench across shop and went in to call
Apple. Since Apple was closed for the Holidays I called TRF again (needed to
vent). After a lot of measuring by me and TRF and several calls back from TRF
we concluded that some PO replaced the original M/C with one from a TR3-6 M/C.
As it turns out the bore in the M/C of the TR cylinders is .050" larger. I
suspect that Apple cross referenced the bore diameter basd on the number cast
into the M/C and not the fact that it came from a '70 Spit. So with the TR
seals all is well, except that it is 10 F here in sunny Alabama.
Based on all of this I would have bought a rebuilt M/C from Apple for $135.00
or so rather than have mine re-sleeved. I just hope that I remember to buy a
TR6 seal kit if I have to do this again.