Mtd YM90 Manuel d'utilisateur télécharger pdf (Page 20)

Replacing the Spark Plug

Use a Champion RDJ7Y spark plug (or equivalent). The

correct air gap is 0.020 inch (0.5 mm). 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 it from the spark plug.

2. Clean 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 0.020 in. (0.5 mm) using a feeler gauge.

See Figure 44.

CAUTION: Do not sand blast, scrape or

clean electrodes. Grit in the engine could

damage the cylinder.

4. Install a correctly-gapped spark plug in the cylinder

head. Tighten by turning the 5/8 inch socket

clockwise until snug.

If using a torque wrench torque to:

110-120 in.•lb. (12.3-13.5 N•m).

Do not over tighten.

0.020 in.

(0.5 mm)

Figure 44

Idle Speed Screw

Figure 43

SECTION 7: MAINTENANCE AND REPAIR INSTRUCTIONS

Carburetor Adjustment

The idle speed of the engine is adjustable through the air

filter/muffler cover. See Figure 43.

NOTE: Careless adjustments can seriously damage your

unit. An authorized service dealer should make

carburetor adjustments.

Check Fuel Mixture

Old and/or improperly mixed fuel is usually the reason for

improper unit performance. Drain and refill the tank with

fresh, properly mixed fuel prior to making any

adjustments. Refer to Oil and Fuel Information.

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

WARNING: The cutting attachment may

spin during idle speed adjustments. Wear

protective clothing and observe all safety

instructions to prevent serious personal

injury.

If, after checking the fuel mixture and cleaning the air

filter, the engine still will not idle, adjust the idle speed as

follows.

1. Start the engine and let it run at a high idle for a

minute to warm up. See Starting/Stopping

Instructions.

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 air filter/muffler cover.

See Figure 43. 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 should solve most engine

problems.

If this is not the case and the following are all true:

• 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: After turning the unit off, make

sure the cutting attachment has stopped

before setting the unit down. This helps

prevent serious personal injury.

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Mtd YM90 Manuel d'utilisateur Page 20

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