The starter rope is wound around a pulley. As the rope is
pulled, the pulley is turned clockwise, The dog retainer
and spring holding the dogs in the cutouts of the pulley
hub allow the dogs to move out of the retracted position.
The sharp edges of the dogs dig into the side of the start-
er cup. The flywheel turns, providing the starting force. As
the rope is released, the dogs retract, allowing the rope
to automatically rewind on the pulley.
1-13. FUEL SYSTEM.
The fuel system is operated by crankcase pressure and
vacuum pulses from the engine crankcase. The pulses
are transferred to the fuel pump diaphragm causing fuel
to be pulled through the inlet flipper of the pump and then
through the outlet flipper of the pump.
The carburetor is a demand-type carburetor. No fuel
flows to the engine until the engine is cranked or operat-
ing. Lower pressure in the throttle bore, or venturi, causes
the main metering diaphragm to depress the inlet liner.
This allows the inlet needle to unseat and permits fuel to
fill the fuel chamber. Fuel flows through the calibrated
holes for low speed or the nozzle for high speed, based
on engine demand and throttle shutter opening, The fuel
pump aids fuel flow by furnishing larger quantities of fuel
to the engine than would be possible without a fuel
pump. The fuel pump cannot move fuel unless the fuel
tank is vented.
Fuel flow through supply openings depends partly on
main (high) or idle (low) adjustment needle settings. Fuel
flow through discharge ports varies with the position of
the throttle shutter. The throttle shutter blocks off or ex-
poses ports to the engine demand and determines the
mode of operation. Fuel flow is enhanced by the throttle
bore, or venturi, a narrowing in opening that causes air to
flow faster and a drop in pressure.
Starting Choke Operation. During starting choke
operation, the choke shutter is closed and the
throttle shutter is open. The fuel passes through
main, primary idle, and secondary idle fuel dis-
Idle Operation. During idle operation. the choke
Intermediate Operation. During intermediate oper-
ation, the choke shutter is open and the throttle shut-
ter is open approximately halfway. Engine speed
and air flow increase as the throttle shutter opens.
The amount of fuel delivered increases as the throttle
shutter uncovers the secondary discharge port, ex-
posing it to engine suction.
High Speed Operation. During high speed opera-
tion, the choke shutter and the throttle shutter are
open. The amount of fuel delivered reaches a maxi-
mum when the throttle is fully open. All discharge
ports are fully exposed to engine demand and to
1-14. REED VALVE ASSEMBLY
The reed valve is between the carburetor and the crank-
case of the engine. It times the injection of the fuel and air
mixture from the carburetor into the crankcase. The reed
valve opens only when pressure in the crankcase drops
to a predetermined point on the compression stroke. The
reed valve maintains contact with the reed plate until
pressure changes in the crankcase. Reed valve travel
away from the plate is limited by the reed stop. When
crankcase pressure increases, the built-in spring action
of the reed valve returns and holds it against the plate.
1-15. IGNITION SYSTEM.
The ignition system consists of six major components:
the flywheel, condenser, coil, breaker points, ignition or
shorting switch, and spark plug.
The rotation of magnets along the outer edge of the fly-
wheel creates a rotating magnetic field that cuts through
the coil winding, building a very strong magnetic field. As
the magnets pass the coil, the magnetic field collapses,
sending a high voltage charge to the spark plug.
shutter is open and the throttle shutter is slightly
open. This prevents fuel from passing through the
secondary idle discharge port.