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ENGINE TOP END 5-29
Cylinder Head
Cylinder Compression Measurement
NOTE
○
Use the battery which is fully charged.
•
Warm up the engine thoroughly, and stop the engine.
•
Remove the spark plug (see Electrical System chapter).
•
Attach the compression gauge [A] and adapter [B] firmly
into the spark plug hole.
Special Tools - Compression Gauge, 20 kgf/cm²: 57001-221
Compression Gauge Adapter, M10 × 1.0:
57001-1458
•
Hold the throttle wide open and crank the engine with the
electric starter or the recoil starter several times.
When the gauge stops rising, stop cranking and read the
gauge.
Cylinder Compression (Usable Range)
Electric Starter: 251 ∼ 456 kPa (2.56 ∼ 4.65 kgf/cm², 36
∼ 66 psi) @380 r/min (rpm)
The following table should be consulted if the obtainable compression reading is not within the us-
able range.
Problem Diagnosis Remedy (Action)
Carbon accumulation on piston,
cylinder head, and in combustion
chamber possibly due to damaged
valve stem oil seal and/or damaged
piston oil rings (This may be
indicated by white exhaust smoke).
Remove the carbon deposits and replace
damaged parts if necessary.
Incorrect cylinder head gasket
thickness.
Replace the gasket with a standard part.
Damaged or missing compression
release cam spring
Replace the spring.
Cylinder
compression
is higher than
usable range
Compression release weights do
not move smoothly.
Replace the compression release unit.
Gas leakage around cylinder head
Replace dam aged gasket and check
cylinder head warp.
Bad condition of valve seating Repair if necessary.
Incorrect valve clearance. Adjust the valve clearance.
Incorrect piston/cylinder clearance Replace the piston and/or cylinder
Piston seizure. Inspect the cylinder and liner and
replace/repair the cylinder and/or piston
as necessary.
Bad condition of piston ring and/or
piston ring grooves
Replace the piston and/or the piston rings.
Cylinder
compression is
lower than usable
range
Compression release weights do
not move smoothly
Replace the compression release unit