I agree with Richard. Scales CRY for the 4-cycle. If you want authenticity, you want sound included. I'm a machine-nut as it is, and those 4-cycle engines are cool machines! However, if you want SIMPLICITY, low price, and raw power to train or do aerobatics and get out of jams, use a two-stroke. They're soooo dependable and trouble-free! My 2 cents.