Yard-Man YM26CO Operator's Manual page 26

MAINTENANCE AND REPAIR INSTRUCTIONS
3. Remove the screw behind the engine cover (Fig. 69).
Fig. 69
4. Disconnect the spark plug wire.
5. Clean dirt from around the spark plug. Remove the
spark plug from the cylinder head by turning a 5/8 in.
socket counterclockwise.
6. Remove the engine cover (Fig. 68).
7. Clean dirt from around the rocker arm cover.
Remove the screw holding the rocker arm cover with
a large flat blade screwdriver or Torx T-25 bit
(Fig. 70). Remove the rocker arm cover and gasket.
Rocker Arm Cover
Spark Plug Hole
Fig. 70
8. Pull the starter rope slowly to bring the piston to the top
of its travel, (known as top dead center). Check that:
• The piston is at the top of its travel while looking in
the spark plug hole (Fig. 70)
• Both rocker arms move freely, and both valves are
closed
If these statements are not true, repeat this step.
9. Slide the feeler gauge between the rocker arm and
the valve return spring. Measure the clearance
between the valve stem and rocker arm (Fig. 71).
Measure both the intake and exhaust valves.
The recommended clearance for both intake and
exhaust is .003 – .006 in. (.076 – 0.152 mm). Use a
standard automotive .005 in. (0.127 mm) feeler gauge.
The feeler gauge should slide between the rocker arm
and valve stem with a slight amount of resistance,
without binding. See Figure 71 and 72.
26
Screw
10. If the clearance is not within specification:
11. Reinstall the rocker arm cover using a new gasket.
12. Reinstall the engine cover. Check alignment of the
13. Reinstall the muffler cover. Slip the rear tab on the
14. Check the spark plug and reinstall. See Replacing
15. Replace the spark plug wire.
Rocker Arms
INTAKE
Feeler Gauge
Fig. 71
Adjusting Nut
.003–.006 in.
(.076–.152 mm)
Fig. 72
a. Turn the adjusting nut using a 5/16 inch (8 mm)
wrench or nut driver (Fig. 72).
• To increase clearance, turn the adjusting nut
counterclockwise.
• To decrease clearance, turn the adjusting nut
clockwise.
b. Recheck both clearances, and adjust as necessary.
Torque the screw to 20–30 in
cover before tightening the screws. Tighten screws.
muffler cover into the engine cover rear slot. Then
slide the remaining slots into the tabs until they snap
into place (Fig. 67).
the Spark Plug.
Adjusting Nuts
EXHAUST
Rocker Arm
Feeler Gauge
Valve Stem
lb (2.2–3.4 N m).
• •