Nearly all the motor buggies at this time had either a one or two-cylinder air cooled engine mounted under the seat. But the Haynes Appeson two-cylinder engine is so large, it has to be water cooled. Each cylinder had its own radiator, or in this case, it had copper heat exchangers on the sides of the vehicle. This engine displaces 274 cubic inches. Larger than some Chevy 8-cylinders.