Cub Cadet ST 100 Operation Manual - Page 14

Spark Plug Service WARNING: DO NOT check for spark with spark plug removed. DO NOT crank engine with spark plug removed. 3. Measure the plug gap with a feeler gauge. Correct as necessary by bending side electrode. See Figure 6-7. The gap should be set to 0.030 in. To ensure proper engine operation, the spark plug must be properly gapped and free of deposits. 1. Remove the spark plug boot and use a spark plug wrench to remove the plug. See Figure 6-6. Electrode Spark Plug 0.030 in. Figure 6-7 Spark Plug Boot 4. Check that the spark plug washer is in good condition and thread the spark plug in by hand to prevent crossthreading. 5. After the spark plug is seated, tighten with a spark plug wrench to compress the washer. Figure 6-6 WARNING: If the engine has been running, the muffler will be very hot. Be careful not to touch the muffler. 2. Visually inspect the spark plug. Discard the spark plug if there is apparent wear, or if the insulator is cracked or chipped. Clean the spark plug with a wire brush if it is to be reused. NOTE: When installing a new spark plug, tighten 1/2 turn after the spark plug seats to compress the washer. When reinstalling a used spark plug, tighten 1/8-1/4 turn after the spark plug seats to compress the washer. IMPORTANT: The spark plug must be securely tightened. An improperly tightened spark plug can become very hot and may damage the engine. 14 Section 6 - Maintenance