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TM 55-1905-220-14-8
4-7.10A. ENGINE - MAINTENANCE INSTRUCTIONS (Continued)
(5) After the exhaust port is fully opened and the intake port is fully closed, further piston travel starts to open
the transfer ports. The compressed fuel/air mixture from the crankcase then travels up the transfer ports and
into the compustion area.
(6) After most of the burned exhaust gases have left the cylinder, an incoming charge of fuel/air mixture
scavenges the combustion area giving it a fresh charge and the cycle is then repeated.
(7) Because lubrication is dependent on the mixing of oil and fuel, it is extremely important that good
quality oil and gasoline are properly mixed. The proper ration of oil to gasoline will prevent possible engine
overheating, piston or cylinder scoring, or eventual engine seizure. Too much oil and not enough gasoline can
lead to incomplete combustion, fouled plugs, carbon buildup, and muffler clogging.
b. Ignition System.
(1) The capacitor discharge ignition (CDI) system consists of a flywheel with four magnets evenly spaced
about the circumference and a stator. The stator serves as a mount for three coils. The exciter coil charges
the capacitor in the CDI igniter; the pulser coil signals the CDI igniter to fire the spark plugs (both spark plugs
fire simultaneously); and the lighting coil supplies current to the voltage regulator.
(2) As the flywheel rotates, an alternating current is induced in the coils mounted on the stator.
(3) The CDI igniter capacitor stores the charge generated by the exciter coil. The amount of charge the
exciter coil gives the capacitor effects the intensity of the spark. Current generated by the pulser coil causes the
capacitor in the CDI igniter to release its stored charge to the ignition coil. The ignition coil primary induces a
high voltage in the secondary winding, and causes a spark to jump
4-386
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