I am not familiar with this engine, but here is a little info. If the engine is not a piston engine, you don't want to let it four cycle for too long as these engines need a bit of heat in order for its parts to mesh correctly. Otherwise, the way to reach your peak rpm with out over heating your engine is as follows. Adjust your engine for its peak rpm and then simply back off of the high needle an 1/8th or even 1/4 turn (rich). While flying the engine will naturally pickup rpm as the engine unloads. I usually will back of the high needle 1/4 turn and fly the plane and attempt to judge if it unloads to its top speed. I will then lean the needle an 1/8 of a turn, fly the engine and compare with the previous flight. If the second flight is not significantly better than the first (@ 1/4 turn rich) I will operate the engine at the richer setting. Of course you must experiment with several different size props, both diameter and pitch if you are looking to getting max performance for a given engine. Good luck.