8" not quite big enough 15" is Whizzer then to about 2.5 , 6" next to it then 2" on engine, check out msrfan another briggs build..........CurtInteresting. I figured it would work. I'm thinking it will be much quieter than the noisy chain drive. Not to mention if a belt pops loose I'm sure the damage will be far less than if the chain pops loose. I'm not sure which pulley sizes to go with. I'm thinking an 8" for the rear an 2-3 inch up front with a belt tensioner will do the trick. Anyway got the idea from Harley sportster set ups. My bike already has the 4stroke huasheng engine and Xhd gear reduction. Only question is what gears will run about the same as the chain gearing I have ? . . Bike runs fast enough.