Johnson's Machine has its own pulley set CNC machined to its specifications, and it's pretty trick. This is the lower pulley (black) with the cam belt pulley sitting on top. The standard setup (this image) requires that the stock belt retainer be used to hold the cog belt on the pulley, and they are often difficult to find. Johnson's (next image) pulley incorporates the retainer, making it impossible to lose. Also, you will notice Johnson's pulley is made for a grooved belt rather than a V-belt. Richard Johnson says dyno tests have proven that the reduction in parasitic friction from switching belts is worth two horsepower on these little motors.