An issue typical of all conversion engines is whether or not they have provision for the axial thrust of the prop on the crankshaft bearings. Chainsaw engines are designed for radial loads due to the saw chain; they do not experience axial loads. If the engine has ball bearings, then it is probably ok, balls can absorb axial loads. If roller or needle bearings are used, an additional thrust washer should be fitted. Good luck.
Best regards, Richard