I had a lot of friends who brazed water jackets around the Cushman engine cylinders and put the engines in midget race cars. Used automobile heater cores as radiators and electric fuel pumps to circulate the coolant (water) through the cooling systems.
A lot of the old guys I raced stock cars with got started in midget racing, and at least one, Joe Shaheen, wound up owning his own speedway, a non-sanctioned outlaw dirt track in Springfield Illinois. Don't hear anything from the midget racers lately.....Joe