ORIGINAL: aspeed
So I just checked a KB. It looks like a TD cyl, and head, and a Surestart backplate. All I would have to do is open up the venturi hole a bit, and maybe make a cutter or something to shave off the piston a bit? I already have a mylar reed someplace too, in a Black Widow or something I can raid. I know we tried a Babe Bee with a 1/8'' bore and on a bladder with 80% nitro that ran very well. TD cyl and plug. I think it swallowed reeds, but that was before the mylar ones were on the scene. Looks like I have to spend/waste some time on the reedies again :-( I can't even use them at the field without a muffler. Maybe my neighbors field is big enough. Oh I still like the AP and ASP's made in the last two or three years. The GZ .049 and CS .049 not so much. Had some nasty Ucktams too. Russian motors are either boogie or bust.
Make a close fitting bushing that has a slit in it to hold the Cox piston in a chuck...
Take a wire and tie off the rod so it doesn't flop around.
Just use a Xacto blade freehand to shave that Leadloy piston. You need good light to see how you're doing. The back side of the blade takes wafer thin shavings with just medium hand pressure.
It's really a fun little "operation" to perform. While yer at it, shorten the skirt to obtain any SPI that you are looking for.
The pistons that were made in the later years don't hold a reset as long as the early models so if you know anything about heat treating the Leadloy piston that might help.