Testing Engine Compression; Spark Plug; Muffler/Spark Arrester - Toro 500 EFI Service Manual

3. Install the spark plug; then install the timing inspec-
tion plug.
4. Place the two tappet covers with O-rings into posi-
tion. Tighten the cap screws to 8 ft-lb.
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.
! 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 a suitable compression tester.
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).
PSI Hot (WOT)
125-145
6. If compression is abnormally low, inspect the fol-
lowing 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 the
Engine/Transmission section.
7. Pour approximately 30 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 the appropriate Engine/Transmission - Top Side
Components).
10
A light brown insulator indicates that the 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.
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 0.5-0.6 mm (0.019-0.024 in.).
PSI Cold (WOT)
100-140
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 con-
tacts the cylinder head.
Clean the spark arrester using the following procedure.
Wait until the muffler cools to avoid burns.

Spark Plug

CAUTION

Muffler/Spark Arrester

! WARNING
1. Open the cargo box and remove the two springs
securing the muffler to the exhaust pipe.
ATV-0051
ATV0052