Testing Engine Compression; Spark Plug; Muffler/Spark Arrester - Arctic Cat DVX 400 2004 Service Manual

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.
! WARNING
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 Compression Gauge (p/n 0444-096).
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). The compression should be
10.0 kg/cm 2 (142 psi).
6. If compression is abnormally low, inspect the
following items.
A. Verify starter cranks engine over at normal
cranking speed.
B. Gauge is functioning properly.
C. Throttle lever in the full-open position.
D. Valve/tappet clearance correct.
E. Valve bent or burned.
F. Valve seat burned.
NOTE: To service valves, see Section 3.
7. Pour 29.5 ml (1 fl oz) of oil into the spark plug hole,
reattach the gauge, and retest compression.
8. If compression is now evident, service the piston
rings (see Section 3).

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.
10
! CAUTION
Before removing the spark plug, be sure to clean
the area around the spark plug. Dirt could enter
engine when removing or installing the spark
plug.
Adjust the gap to 0.7 - 0.8 mm (0.028 - 0.032 in.). Use a
feeler gauge to check the gap.
When installing the spark plug, tighten to specifications.

Muffler/Spark Arrester

The muffler has a spark arrester which must be periodi-
cally cleaned. At the intervals shown in the Periodic
Maintenance Chart, clean the spark arrester using the fol-
lowing procedure.
! WARNING
Wait until the muffler cools to avoid burns.
1. Remove the three Allen-head cap screws securing
the spark arrester to the muffler; then remove the
spark arrester.
ATV-0051
ATV0052B