OK take no.2
It is a series 75 K&B shiney case with a steel.790 bore ,no discernible taper with a moderate? factory cross hatch pattern.
All parts are new old stock. Many thanks to those who have replied so far.
Jim
Hi JIm
Given that, If you want to break-in very careful, I would setup the Ring gap very tight from .001 to almost zero gap. You can turn it over by hand with light oil, in both directions very quickly for several minutes, Then run it only a a bench very sloppy rich for 1 to 3 minutes , Do this about 10 runs, Then start to lean it a a Lean 4 stroke. after a few more runs, pinch the fuel tube to let it burst 2 cycle for a couple of seconds,
Then last step, Run it into a 2 cycle for 15 seconds back to a 4 cycle, for 30 seconds and repeat
This will be the way to get a very good fit, All this based on a fairly good cross hatch but into the sleeve
Do NOt rush it
The main problem you may find is getting rings that have less than 5 to 12 thousands gap...new
I would use 25 to 28% oil with 1/2 synthetic 1/2 castor oil
Randy