Testing Engine Compression; Spark Plug(S) - Arctic Cat 500 Service Manual

 NOTE: Rotating the valve adjuster dial counter-
clockwise will open the valve/tappet clearance by
0.05 mm (0.002 in.) per mark.
E. While holding the adjuster dial at the proper
clearance setting, tighten the jam nut securely
with the valve adjuster handle.
F. Rotate the engine 270° to the TDC position of the
rear cylinder; then repeat steps A-E for the rear
cylinder.
3. Install the timing inspection plug; then on the 1000
models, remove the cap screw and install the crank-
case end cap.
4. Place the tappet covers into position making sure the
proper cap screws are with the proper cover. Tighten
the cap screws securely.
5. Install the spark plug(s).
Testing Engine
Compression
To test engine compression, use the following procedure.
1. Remove the high tension lead(s) from the spark
plug(s).
2. Using compressed air, blow any debris from around
the spark plug(s).
! WARNING
Always wear safety glasses when using compressed
air.
3. Remove the spark plug(s); then attach the high ten-
sion lead(s) to the plug(s) and ground the plug(s) on
the cylinder head(s) well away from the spark plug
hole(s).
4. Attach the Compression Tester Kit.
 NOTE: The engine should be warm (operating tem-
perature) and the battery fully charged for an accu-
rate compression test. Throttle must be in the
wide-open throttle (WOT) position. In the event the
engine cannot be run, cold values are included.
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).
COMPRESSION
Model PSI Hot (WOT)
500
550
700
1000 (Front)
1000 (Rear)
PSI Cold (WOT)
95-115 N/A
120-140 80-120
125-145 100-140
125-145 80-120
165-185 150-190
6. If compression is abnormally low, inspect the
following items.
A. Verify starter cranks engine over at normal speed
(approximately 400 RPM).
B. Gauge functioning 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.
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 Engine/Transmission).

Spark Plug(s)

A light brown insulator indicates that a plug is correct. A
white or dark insulator indicates that the engine may need
to be serviced. To maintain a hot, strong spark, keep the
plug free of carbon.
CAUTION
Before removing a 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 correct specification (see General Infor-
mation for proper type and gap). Use a feeler gauge to
check the gap.
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