Air Filter Maintenance; Carburetor Adjustment; Rocker Arm Clearance - MTD 890 Owner's Manual

5. Refill the crankcase with 100 ml (3.4 floz) of SAE 30
SF, SG, SH oil.
6. Replace the oil fill plug/dipstick.
7. Reconnect spark plug boot.

AIR FILTER MAINTENANCE

Cleaning the Air Filter
WARNING: To avoid serious personal injury, always
turn your trimmer off and allow it to cool before you
clean or do any maintenance on it.
Clean and re-oil the air filter every 10 hours of operation.
It is an important item to maintain. Not maintaining the
air filter will VOID the warranty.
1. Open the air filter cover. Push the tab on the right
side of the cover in, pull the air filter cover out and to
the left (Fig. 36).
NOTE: It may be necessary to remove the fuel cap to
completely remove the air filter cover
2. Remove the air filter (Fig. 36).
3. Wash the filter in detergent and water (Fig. 37). Rinse
the filter thoroughly and allow it to dry.
4. Apply enough clean SAE 30 motor oil to lightly coat
the filter (Fig. 38).
5. Squeeze the filter to spread and remove excess oil
(Fig. 39).
6. Replace the filter.
NOTE: If the unit is operated without the air filter, you
will VOID the warranty.
7. Reinstall the air filter cover. Position the hooks on the
left side of the air filter cover into the slots at the left
side of the back plate (Fig. 40).
NOTE: It may be necessary to remove the fuel cap to
reinstall the air filter cover
8. Swing the cover to the right until the tab on the air
filter cover snaps into place in the slot on the back
plate (Fig. 40).
9. Replace the fuel cap, if removed.

CARBURETOR ADJUSTMENT

The idle speed of the engine is adjustable. An idle
adjustment screw is reached though a hole in the top of
the engine cover (Fig 41).
NOTE: Careless adjustments can seriously damage your
unit. An authorized service dealer should make
carburetor adjustments.
Check Fuel
Old fuel is usually the main reason for the unit not
running properly. Drain and refill the tank with clean,
fresh unleaded fuel prior to doing any adjustments. Refer
to Oil and Fuel Information.
26
MAINTENANCE AND REPAIR INSTRUCTIONS
Clean Air Filter
The condition of the air filter is important to the operation
of the unit. A dirty air filter will restrict air flow and
change the air/fuel mixture. This is often mistaken for an
out of adjustment carburetor. Check the condition of the
air filter before adjusting the idle speed screw. Refer to
Air Filter Maintenance.
Adjust Idle Speed Screw
WARNING: The cutting attachment may be spinning
during idle speed adjustment. Wear protective
clothing and observe all safety instructions to prevent
serious personal injury.
If after checking the fuel and cleaning the air
filter the engine still will not idle, adjust the idle speed
screw as follows.
1. Start the engine and let it run at a high idle for a
minute to warm up.
2. Release the throttle trigger and let the engine idle. If
the engine stops, insert a small phillips or flat blade
screwdriver into the hole in the engine cover
(Fig. 41). Turn the idle speed screw in, clockwise,
1/8 of a turn at a time (as needed) until the engine
idles smoothly.
NOTE: The cutting attachment should not rotate when
the engine idles.
3. If the cutting attachment rotates when the engine
idles, turn the idle speed screw counterclockwise 1/8
of a turn at a time (as needed), to reduce idle speed.
Checking the fuel mixture, cleaning the air filter, and
adjusting the idle speed screw should solve most engine
problems.
If not and:
• The engine will not idle
• The engine hesitates or stalls on acceleration
• There is a loss of engine power
Have the carburetor adjusted by an authorized service
dealer.
WARNING: When the unit is turned off make sure the
cutting attachment has stopped before the unit is set
down to prevent serious personal injury.

ROCKER ARM CLEARANCE

This requires disassembly of the engine. If you feel
unsure or unqualified to perform this, take the unit to an
authorized service center.
NOTE: Inspect the valve to rocker arm clearance with a
feeler gauge after the first 10 hours of operation
and then every 25 hours of operation thereafter.
• The engine must be cold when checking or adjusting
the valve clearance.