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CHAPTER 5 The Two-Stroke Cycle Engine
Copyright Goodheart-Willcox Co., Inc.
Pawl
The clutch connection between the starter and
crankshaft uses pawls to transmit rotation. A
pawl is a plastic or metal piece that transmits
torque from an input (driving) component to an
output (driven) component. A two-stroke starter
may use one or two pawls. The pawl may be
mounted on the input component or the output
component.
An example of the pawls mounted on the
input component is shown in Figure 5-26A.
Two pawls are mounted onto the starter pulley.
The pawls fit into a starter cup on the flywheel,
Figure 5-26B. When the starter rope is pulled,
the pawls swivel outward and catch the inside of
the starter cup, causing the flywheel to rotate.
An example of the pawls mounted on the
output component is shown in Figure 5-27.
Two pawls are mounted onto the flywheel. Two
flats on the bottom of the starter pulley drive
the pawls, causing the flywheel to rotate. Once
the flywheel increases speed, centrifugal force
slings the pawls outward so they do not contact
the starter pulley. Notches cut into the cooling
fins provide space for the pawls to be kept when
the flywheel is rotating.
PTO
The PTO portion of the engine is where the two-
stroke engine performs “work.” The power take-
off is the part of the engine where the rotational
output from the engine is harnessed to perform
tasks like cutting trees, blowing leaves, or trim-
ming grass.
CAUTION
Always read the owner’s manual for each piece
of equipment for the correct starting proce-
dure. On some engines, care must be taken not
to pull the rope to the end, as this may damage
the rewind assembly. Also, avoid letting go of
the rope and letting it snap back to the rewind
housing. This impact could also damage the
rewind housing.
SHOP PRACTICE
Always follow the service manual for the cor-
rect procedure to replace the starter rope. The
replacement rope must be the correct type,
diameter, and length.
A B
Starter rope Pawls Starter pulley Starter cup Flywheel
Goodheart-Willcox Publisher
Figure 5-26. In this rewind starter assembly, the pawls are mounted on the starter pulley. When the
rope is pulled outward, the pawls on the pulley pivot outward and engage the ribs on the inside of the
starter cup. A—Pulley and pawls. B—Flywheel and starter cup.