Replacing The Spark Plug; Spark Arrestor Maintenance - MTD 890 Owner's Manual

• This task should be performed inside, in a clean, dust
free area.
1. Remove the muffler cover by pressing down on the
corner with a flat blade screwdriver (Fig. 42). Slide
the notches on the sides of the muffler cover over
the tabs on the engine cover and remove.
2. Remove the two (2) screws on top of the engine
cover with a Flat-head or T20 screwdriver (Fig. 43).
3. Remove the screw on back of the engine cover
(Fig. 44).
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.
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 T25 bit
(Fig. 45). Remove the rocker arm cover and gasket.
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. 45).
• Both rocker arms move freely, and both valves are
closed.
If not, repeat step 8.
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 46).
Do both intake and exhaust valves.
The recommended clearance for both intake and
exhaust is .076 - 0.152 mm (0.003 – .006 in). Use a
standard automotive 0.127 mm (0.005 in) feeler gauge.
The feeler gauge should slide between the rocker arm
and valve stem with a slight amount of resistance,
without binding (Fig. 47).
10. If the clearance is not within specification:
a. Turn the adjusting nut using a 5/16 inch wrench or
nut driver (Fig. 46).
• 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 2.2–3.4 N
MAINTENANCE AND REPAIR INSTRUCTIONS
m ( 20–30 in lb).
• •
NOTE: A rocker arm cover gasket can be purchased
from your local authorized dealer.
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 (Fig. 42).
14. Check the spark plug and reinstall. See Replacing
the Spark Plug.
15. Replace the spark plug wire.

REPLACING THE SPARK PLUG

Use only genuine replacement spark plugs. The correct
air gap is 0.655mm (0.025 in). Remove the plug after
every 25 hours of operation and check its condition.
1. Stop the engine and allow it to cool. Grasp the plug
wire firmly and pull the cap from the spark plug.
2. Clean dirt from around the spark plug. Remove the
spark plug from the cylinder head by turning a 5/8 in.
socket counterclockwise.
3. Replace cracked, fouled or dirty spark plug. Set the
air gap at 0.655 mm (0.025 in) using a feeler gauge
(Fig. 48).
4. Install a correctly gapped spark plug in the cylinder
head. Tighten by turning the 5/8 in. socket clockwise
until snug.
If using a torque wrench torque to;
12.3–13.5 Nm (110–120 in.•lb.).
Do not over tighten.

SPARK ARRESTOR MAINTENANCE

1. Remove the muffler cover. See Rocker Arm
Clearance.
2. With a flat blade screwdriver or Torx T20 bit, remove
the screw attaching the spark arrestor cover to the
muffler (Fig. 49).
3. Pull the tab on the spark arrestor cover out of the
muffler. Remove the spark arrestor cover.
4. Remove the spark arrestor screen from the spark
arrestor cover.
5. Clean the spark arrestor screen with a wire brush, or
replace.
6. Reinstall the spark arrestor screen, spark arrestor
cover, and screw.
27