How to Change the Spark Plug in a John Deere STX38
- 1). Raise the engine cover on the tractor, and tilt it forward. Locate the spark plug and ignition coil wire on the front of the engine. Remove the coil wire from the spark plug by hand.
- 2). Remove the spark plug with a 3/8-inch drive ratchet and a spark plug socket. Turn the plug counterclockwise with the ratchet until it is completely removed from the engine.
- 3). Measure the plug gap on the new spark plug, using spark plug gap tool or a set of feeler gauges. Set the spark plug gap to 0.30 for the engine model CV16. Set the spark plug gap at 0.40 for engine models CV11 through CV15, 460, and 490. The engine model number is on the serial plate under the engine cover.
- 4). Insert the new spark plug using your fingers to thread the plug. Tighten the spark plug with a 3/8-inch drive torque wrench and spark plug socket, between 96 and 120 inch-pounds (8 to 10 foot-pounds).
- 5). Install the coil wire onto the new spark plug, making sure it clicks into place.
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