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ignited, the expanding gases force the piston to move inward toward the crankshaft during
the power stroke.
The rocker box cast in the outer end of the head has a surrounding flange which is
machined flat. The pressed steel rocker cover is sealed to the flange by a gasket and
retained by six Fillister head screws. Three bosses cast in the rocker box are bored in a
horizontal line at right angles to the cylinder axis to form rocker shaft supports. Valve
ports in the head open downward into two flanges, each provided with two studs. Bronze
alloy intake valve guides and Ni-resist alloy exhaust valve guides are pressed into the
cylinder head from the bottom of the rocker box into the valve chambers in line with the
valve seats. Silchrome alloy intake valve seat inserts and Stellite exhaust valve seat inserts
are shrunk into counterbores in the combustion chamber surface.
A 1/8"-NPT port is machined through the upper wall of the intake valve chamber for an
optional primer jet, which may be installed by the owner. The port is sealed by a pipe plug
from the factory. An external base flange below the cylinder barrel fins is mounted flat and
drilled for the six crankcase studs to which the assembly is attached by flanged hex nuts.
From the base flange, the cylinder skirt extends inward through the crankcase wall
opening, as a pilot. A rubber packing ring, placed around the cylinder skirt and against the
flange, is compressed in a chamfer around the pad opening and prevents oil leakage.
Cylinder cooling fins are tapered toward the base for weight reduction.
Push rod tubes are comprised of a push rod to crankcase adapter and pushrod tubes fitted
with O-rings at the crankcase adapter and cylinder head; springs fitted to a flange on the
outside of the pushrod tube apply constant downward pressure on the lower O-ring to
prevent leaks.
O-200-D & X Series Engine Installation and Operation Manual
3 January 2017
ROCKER ARM
ROCKER ARM
VALVE
VALVE
SPRING KEY
SPRING KEY
VALVE
VALVE
SPRING
SPRING
RETAINER
RETAINER
VALVE SPRING
VALVE SPRING
SEAT
SEAT
VALVE GUIDE
VALVE GUIDE
VALVE SEAT
VALVE SEAT
INSERT
INSERT
EXHAUST VALVE
EXHAUST VALVE
INTAKE VALVE
INTAKE VALVE
Figure 2-10. Cylinder Features
Engine Description
INNER SPRING
INNER SPRING
OUTER SPRING
OUTER SPRING
COOLING FINS
COOLING FINS
2-15
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