I think you meant divide by .061 !! Thanks for the help guys, assuming I was accurate measuring the stroke, (the bore is easy) it's a 21cc

I was visiting the local mom and pop lawn mower shop today, and I found out there are no parts available for it, not even a piston ring, they said McCulloch has changed names so many times, and they don't have access to any parts for real old stuff, (they said this one is Pre-1987) They didn't think too highly of it anyway, their choice is stihl or tanaka, has anyone heard of tanaka ? They had a nice looking unit there, electric start, big carb, 4 bolts holding the cylinder on, nice model engine type backplate mount already there !! So I brought it home, (the addiction has begun ) He said it was a very expensive trimmer, I paid $25 for it. It was missing the starter battery, and a fuel tank and some of the shrouds, But I rigged up a battery and fuel system and had it running in no time, then starting stripping it down. I was very excited at first, since the cylinder is held on with 4 bolts, and it has the "normal" backplate and mount built in. The coil is mounted dead center, on two very nice cast lugs, with webbing, so I can grind away almost all of the flywheel housing and still have a strong mount for the coil, that will look nice too The flywheel on this one is backwards too, but the crankshaft is so long, I can slide on a spacer and probably install a prop with no adapter necessary. This one has a ball bearing on the crankshaft, BUT ONLY ONE !!! is that normal? with the piston at BDC (not up in the cylinder for stability) you can actually wiggle the crankshaft a little in the bearing, it's not lose per se, but with only one bearing, it kinda "pivots" since there is no other support, I'm not sure about this one. Also the carb is plastic, it's a walbro, but a plastic housing, and the throttle is a barrel type, similar to R/C carbs, not a butterfly, These things are intriguing, I'll take some pics, and hopefully someone can comment Oh, if this helps, the trimmer I bought was a Tanaka AST-5000