The AOMC used to have a 5hp "fun class" for the young kids to run at their meets. One "stock" 5hp motor had a big carb, counter weighted crank, lightened crank / flywheel, couple of extra reeds per cylinder and some real high ports.......

The bathtub guys in the North West run a "stock" Suzuki 8hp motor. Several of these have had a ton of work done to them. They sure look stock on the outside.....

Michael