An internal combustion engine is disclosed. The internal combustion engine includes a head, a first and second cylinders, a first and second doubled-end pistons, a wrist pin, a connecting rod, and a crankcase. The first and second doubled-end pistons are disposed within the first and second cylinder, respectively. The wrist pin and the connecting rod are connected to the first and second doubled-end pistons. The crankcase contains a crankshaft connected to the connecting rod. The head, which is coupled to the first and second cylinders, includes a first and second spark plugs for associating with first ends of the first and second doubled-end pistons, respectively. The crankcase includes a third and fourth spark plugs for associating with second ends of the first and second doubled-end pistons, respectively.