RE: AVOID THIS ENGINE AT ALL COST!!!!!
I've got/had:
OS FX .25- easy starts, good power, runs great
Evolution .45 trainer- very reliable, easy starts (1 or 2 flips always), good power, easy to tune
OS .46 AX- consistant, screamer, runs great (as they are a new design I can't comment on longevity)
Saito .56- runs good, good power, fuel efficient, very reliable slow idle (love that sound)
Evolution NT .61- easy starts, very reliable, good power
Thunder Tiger .91 FS- easy starts, very good power, good idle, reliable
Only bad experience was with a TT .25 GP. Overall they are probably an ok engine for the $$ I just got a bad one. That can happen with any brand.