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Two-Stroke Engines
Copyright Goodheart-Willcox Co., Inc.
The internal visual evaluation of the engine is the
last process because the cylinder, crankcase, pis-
ton, and crankshaft must be disassembled for
evaluation.
Once the evaluation is complete and the deci-
sion is made to repair the engine, the repairs
must be made correctly using a service manual
and OEM replacement parts. The equipment
must be adjusted correctly.
Engine Exterior
Engine evaluation begins by inspecting for faults
immediately visible on the outside of the two-
stroke equipment and without removing any
components. This process is similar to the visual
inspection performed at the beginning of the trou-
bleshooting process, but involves both looking for
faults visually and testing components for faults.
The following list identifies typical areas to be
evaluated on the exterior of two-stroke equipment:
• Engine covers.
• Fasteners.
• Safety labels and warning labels.
• Starter rope and rewind operation.
• Throttle trigger operation.
• Chain brake operation.
• Deflectors and/or shields condition.
• Attachment condition.
• AV (anti-vibration) system.
Check all engine covers for cracks or pieces
that are broken and missing, Figure 9-11. The
two-stroke engine in Figure 9-12 is missing its
engine cover. Without this cover, the cooling air
from the flywheel cannot be ducted over the cyl-
inder to keep it cool. As a result, the engine will
overheat. Inspect the engine for missing fasten-
ers and use the appropriate tools to check for
loose fasteners.
Safety labels and warning labels are import-
ant for the operator’s safety. Make a note of the
labels that are missing and those that are dam-
aged to the point where they are difficult to read.
These will need to be replaced before the unit is
returned to the customer.
Pull the starter rope slowly out to its com- r
plete length. Check the rope for fraying close
to the end of its travel. The rope in Figure 9-13
Cracked
rewind housing
Missing
fastener
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Figure 9-11. This starter housing is cracked and
missing a fastener. These problems could inter-
fere with starter operation and cause vibrations.
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Figure 9-12. An engine cover directs cooling air
from the flywheel over the cylinder cooling fins.
Since this string trimmer’s engine cover is miss-
ing, it is prone to overheating.
Frayed rope
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Figure 9-13. Pull the rope slowly to its full extent
to see if the rope is frayed or damaged. Do not
let the rope snap back. Retract it slowly. The rope
should retract fully to the handle.