3to 11hp 4-cycle l-head engines - Small Engine Suppliers

COMPONENTS
The cylinder block houses the piston, valves and along with the cylinder cover all the internal components. The block
is a one piece diecast aluminum alloy or cast iron cylinder casting (diag. 10).
The piston transmits the force of the burning and expanding gases through the connecting rod to the crankshaft.
The piston rings provide the seal between the cylinder wall and the piston. The rings keep the combustion pressures
from entering the crankcase and also wipe the oil off the cylinder wall and return it to the sump.
The connecting rod assembly is the link between the piston (piston pin) and the crankshaft.
The cylinder head is a one piece aluminum alloy or cast iron casting that is bolted to the top of the cylinder block. The
many fins provide cooling for the engine.
The crankshaft converts the up and down piston movement to the rotational force (torque) by an offset crankpin or
rod journal.
The camshaft lobes raise and lower the lifters at the proper time to allow air and fuel in and exhaust out of the
cylinder. Teeth on the camshaft gear time the camshaft to the crankshaft.
The valves allow air-fuel mixture to enter the cylinder and exhaust gases to exit. The valves provide a positive seal
when closed.
The valve springs return the valves to the closed position and must be strong enough to maintain valve lifter and cam
lobe contact. The valve retainers lock the spring to the valve stem.
The valve lifters maintain contact on the camshaft and push the valves open.
The crankcase breather is a one way check valve that allows air out and prevents air from coming in. It allows the
engine to develop a partial vacuum in the crankcase during operation.
The cylinder cover (or flange on verticals) provides the bearing surface for the power take off (P.T.O.) end of the
crankshaft and camshaft. This bolted on cover is removed to provide access to all internal components.
The oil pump (vertical shaft only) consists of a steel plunger and a nylon housing that rides on the camshaft eccentric.
The flywheel provides the mass to smooth the effects of one power stroke every other crankshaft revolution. Flywheels
are made of aluminum alloy or cast iron. The flywheel fins act as a fan to cool the engine.
CYLINDER COVER
CYLINDER BLOCK
CYLINDER HEAD
PISTON RINGS
VALVES
PISTON
CONNECTING
ROD
VALVE SPRINGS
CRANKCASE BREATHER
VALVE LIFTERS
CRANKSHAFT
CAMSHAFT
FLYWHEEL
10
74