9
Testing Engine
Compression
NOTE: The engine should be warm (operating tem-
perature) and the battery fully charged for an accu-
rate compression test. The throttle must be in the
wide-open throttle (WOT) position. In the event the
engine cannot be run, cold values are included.
NOTE: The seat, seat back, and seat base must be
removed for this 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 Tester Kit.
5. While holding the throttle in the full-open position,
crank the engine over with the electric starter until
the gauge stops climbing (five to 10 compression
strokes).
6. If compression is abnormally low, inspect the
following items.
A. Starter cranks engine over.
B. Gauge is functioning properly.
C. Throttle in the full-open position.
D. Valve/tappet clearance correct.
E. Engine warmed up.
F. Intake obstructed.
NOTE: To service top-side components, see Engine/
7. Pour approximately 30 ml (1 fl oz) of oil into the
spark plug hole, reattach the gauge, and retest com-
pression.
8. If compression is now evident, service the top end
(see the appropriate Engine/Transmission - Top-Side
Spark Plug
A light brown insulator indicates that the plug and fuel/
air ratio are 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.
ATV-0051
On the 700, adjust the gap to 0.5-0.6 mm (0.019-0.024
in.). On the 500, adjust the gap to 0.7-0.8 mm (0.028-
0.031 in.).
ATV0052
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.
Muffler/Spark Arrester
Clean the spark arrester using the following procedure.
1. Remove the cap screws securing the spark arrester
screen assembly to the muffler; then loosen and
remove the spark arrester. Account for a gasket and
wave washer.
! WARNING
Always wear safety glasses when using compressed
air.
PSI Hot (WOT)
PSI Cold (WOT)
125-145 (700)
100-140 (700)
213 (500) approx.
N/A (500)
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.
! WARNING
Wait until the muffler cools to avoid burns.
Summary of Contents for HDX 500 2017
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