The best gassers out there in the 50CC, 30CC would be DA, DL, DLE....good reliable engines. everyone stocks them so it is easy to get parts and support...
Since you're new to gassers please use an optic kill switch......it will shut off the engine in case of a power failure on the airplane...it has a small section of fiber optic to help reduce noise ( interference ) from your ignition...plus it gives you an additional way to kill the engine from your transmitter