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Fig. 17

0.025 in.

(0.635 mm)

ADJUSTING THE IDLE SPEED

If the engine will not idle properly:

1. Start the engine. Refer to Starting and Stopping.

2. Move the cruise control to the LO (slow) position and let the

engine idle.

• If the engine stops, increase the idle speed. Use a small

Phillips screwdriver to turn the idle speed screw clockwise,

1/8 of a turn at a time, until the engine idles smoothly (Fig. 16).

MAINTAINING THE SPARK PLUG

1. Stop the engine and allow it to cool. Grasp the spark plug boot

firmly and pull it from the spark plug.

2. Clean around the spark plug. Remove the spark plug from the

cylinder head with a 5/8-inch socket, turning counterclockwise.

3. Inspect the spark plug. If the spark plug is cracked, fouled or

dirty, replace it with replacement part #794-00097, a Champion

QDJ7J or an equivalent spark plug.

4. Use a feeler gauge to set the air gap at 0.025 in. (0.635 mm)

(Fig. 17).

5. Install the spark plug in the cylinder head. Tighten the spark plug

with a 5/8-inch socket, turning it clockwise until snug.

NOTE: If using a torque wrench, torque to:

110-120 in.•lb. (12.3-13.5 N•m). Do not over tighten.

6. Reattach the spark plug boot.

WARNING:

Do not sand blast, scrape or clean spark plug

electrodes. Grit in the engine could damage the cylinder.

Fig. 16

Idle Speed Screw

Troy-Bilt TB51BP User Manual

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