Did a comparison of 20cc engines for weight, price and power, chart attached. Looks like the Saito, the only four stroke, is the most expensive, only 2 oz heavier than the lightest, and appears small enough to fit the Hog Bipe. Have to start saving my pennies. Saw a used one on ebay starting price 270, will continue to look for a good used one. Any advice on any, or others, appreciated.