MTD PRO MP426CS Operator's Manual page 18

SECTION 7: MAINTENANCE AND REPAIR INSTRUCTIONS
3. Remove the screw behind the engine cover. See
Figure 38.
Figure 38
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. See Figure 37.
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. See
Figure 39. Remove the rocker arm cover and gasket.
Rocker Arm Cover
Spark Plug Hole
Figure 39
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. See Figure 39.
• 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. See Figure 40. 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 40.
Screw
18
Rocker Arms
INTAKE
Feeler Gauge
Figure 40
Adjusting Nut
.003–.006 in.
(.076–.152 mm)
Figure 41
10. If the clearance is not within specification:
a. Turn the adjusting nut using a 5/16 inch (8 mm)
wrench or nut driver. See Figure 41.
• To increase clearance, turn the adjusting nut
counterclockwise.
• To decrease clearance, turn the adjusting nut
clockwise.
b. Recheck both clearances, and adjust as necessary.
11. Reinstall the rocker arm cover using a new gasket.
Torque the screw to 20–30 in
12. Reinstall the engine cover. Check alignment of the
cover before tightening the screws. Tighten screws.
13. Reinstall the muffler cover. Slip the rear tab on the
muffler cover into the engine cover rear slot. Then
slide the remaining slots into the tabs until they snap
into place. See Figure 36.
14. Check the spark plug and reinstall. See Replacing
the Spark Plug.
15. Replace the spark plug wire.
Adjusting Nuts
EXHAUST
Rocker Arm
Feeler Gauge
Valve Stem
lb (2.2–3.4 N m).
• •