I bought a complete engine out of a guys shed a month ago, it had been sitting there since the '70s!
It has Single Port heads on it........I want to use them in my next motor. Dunno what I'll do with the rest!
For chamber size, I have heard everywhere around the 40s, but 42cc and 46cc seem to come up a lot whenever I try to find the info.
It's not exact, but better than nothing I spose.