9
TR197
9. Install the crankcase cover aligning the oil hole with
the oil passage in the crankcase.
Testing Engine
Compression
To test engine compression, use the following procedure.
1. Remove the high tension lead from the spark plug.
2. Using compressed air, blow any debris from around
the spark plug.
3. Remove the spark plug; then attach the high tension
lead to the plug and ground the plug on the cylinder
head well away from the spark plug hole.
4. Attach the Compression Gauge.
NOTE: The engine must be warm and the battery
must be fully charged for this test.
5. While holding the throttle lever in the full-open posi-
tion, crank the engine over with the electric starter
until the gauge shows a peak reading (five to 10
compression strokes).
NOTE: The compression should be within a range
of 210-230 psi in the full-open throttle position.
6. If compression is abnormally low, verify the follow-
ing items.
A. Starter cranks engine over normally.
B. Gauge functions properly.
C. Throttle lever in the full-open position.
D. Valve/tappet clearance correct.
E. Engine warmed up.
F. Intake not restricted.
NOTE: To service valves, see Engine/Transmission -
Servicing Top-Side Components.
7. Pour approximately 30 ml (1 fl oz) of oil into the
spark plug hole, attach the gauge, and test compres-
sion.
8. If compression is now evident, service the piston
rings (see Engine/Transmission - Servicing Top-Side
Components).
Spark Plug
A light brown insulator indicates that the plug is correct.
A white or dark insulator indicates that the engine may
need to be serviced or the carburetor may need to be
adjusted. To maintain a hot, strong spark, keep the plug
free of carbon.
ATV-0051
Adjust the gap to 0.6 mm (0.024 in.) for proper ignition.
Use a wire feeler gauge to check the gap.
ATV0052D
When installing the spark plug, make sure to tighten it
securely. A new spark plug should be tightened 1/2 turn
once the washer contacts the cylinder head. A used spark
plug should be tightened 1/8-1/4 turn once the washer
contacts the cylinder head.
! WARNING
Always wear safety glasses when using compressed
air.
CAUTION
Before removing the spark plug, make sure to clean the
area around the spark plug. Dirt could enter engine
when removing or installing the spark plug.
