kochj
Or scrap the 4 stroke use a two stroke
And use some sort of power valve like the motocross bikes use.
THis power valve is a mechanical device that lower the exhaust port for the purpose of get more power (not on of motor)at low revs. Normally the engine is built to a narrow powerband and the above widens said powerband.
Clever device!!!! Can it be built into a hobby engine??????
Best regards