Poulan (craftsman) makes some saws in the 50--60cc range.

I've done 2 of the Poulan 54cc engines. Good power. You do have to cut the gas and oil tanks away, and then dremel it smooth. But, it's not hard--just a little time involved.

Are you interested in a 62cc Pioneer engine? Side reed induction. (Think 3W-70.) Already cut it apart--you just need to finish converting it. Replace bearings, seals, and get an ignition for it.

Email or PM me if your interested.