PRINCIPAL ENGINE PARTS
Timing gears. The gear at the front of the camshaft has twice as many teeth as the crankshaft gear that drives it. Hence it revolves only half as fast as the crankshaft gear. We need this speed relation in four-cycle engines; the crankshaft must revolve twice to make the pistons complete their four functions; only one revolution of the camshaft will open and close all the valves. These two gears are the «timing gears». When correctly meshed together they will give the correct relation between the position of any piston and the time of the opening and closing of the valves. On these timing gears you will find punch marks which tell when they are meshed correctly.
Flywheel. The flywheel, which is bolted to the rear of the crankshaft, acts as a balance wheel to make the engine run evenly. Also in most of engines the main clutch- the principal power control — is installed at the rear of the flywheel.
Crankcase. The crankshaft is fully enclosed in an oiltight housing. Part of this housing is the lower portion of the engine block. A removable oil pan or reservoir is bolted the bottom of the engine block to complete the enclosure. This reservoir contains the oil supply for the engine; the pump, which circulates oil to all engine parts, is immersed in this oil supply.