Valve/Tappet Clearance; Testing Engine Compression; Spark Plug - Arctic Cat ATV 300 Utility/DVX 300 2011 Service Manual

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Valve/Tappet Clearance

To check and adjust valve/tappet clearance, use the fol-
lowing procedure.
 NOTE: The seat assembly, side panels, and gas
tank must be removed for this procedure.
1. Remove the timing inspection plug; then remove the
cylinder head cover (see Engine/Transmission -
Removing Top-Side Components).
2. Rotate the crankshaft so the "T" mark on the fly-
wheel aligns with the index mark on the right-side
crankcase cover.
 NOTE: At this point, the round hole in the camshaft
gear should be up.
3. Place Tappet Adjuster onto the jam nut securing the
tappet adjuster screw; then rotate the adjuster dial
clockwise until the end is seated in the tappet
adjuster screw.
4. While holding the adjuster dial in place, use the
adjuster handle and loosen the jam nut; then rotate
the tappet adjuster screw clockwise until friction is
felt.
5. Align the adjuster handle with one of the marks on
the adjuster dial.
6. While holding the adjuster handle in place, rotate the
adjuster dial counterclockwise until proper valve/
tappet clearance is attained.
 NOTE: Refer to the appropriate specifications in
Engine/Transmission for the proper valve/tappet
clearance.
 NOTE: Rotating the adjuster dial counterclockwise
will open the valve/tappet clearance by 0.05 mm
(0.002 in.) per mark.
7. While holding the adjuster dial at the proper clear-
ance setting, tighten the jam nut securely with the
valve adjuster handle.
8. Place the cylinder head cover with a new O-ring into
position; then tighten the cover securely.
9. Install the timing inspection plug.
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.
Always wear safety glasses when using compressed
air.
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 gauge from Compression Tester Kit.
 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.
B. Gauge functions properly.
C. Throttle lever in the full-open position.
D. Valve/tappet clearance correct.
E. Valve not bent or discolored.
F. Valve seat not discolored.
 NOTE: To service valves, see Engine/Transmission.
7. Pour 29.5 ml (1 fl oz) of oil into the spark plug hole,
attach the gauge, and test compression.
8. If compression is now evident, service the piston
rings (see Engine/Transmission).
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.
KM703
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Manual
Table of Contents
Testing Engine
Compression
! WARNING

Spark Plug

9