Checking for a good spark at the spark plug on an ATV engine can help diagnose a poor running, or non-running condition. A weak spark can cause poor performance, hard starting and a rough idle. Checking the spark by using a timing light with an inductive pick-up will tell you if there is power going through the plug wire, but will give no indication of the quality of the spark or if the plug is carbon-fouled and not sparking at all. Removing a plug from the ATV’s engine and observing the spark is the only way to tell.
Things You'll Need
- Shop rag
- Spark plug socket
Park the ATV on firm, level ground, preferably in a shady spot or at least out of direct sunlight. Turn the fuel petcock to the “Off” position. Set the parking brake and put the transmission in neutral.
Clean the area around the spark plug with a shop rag or compressed air to remove dirt. Pull the spark plug wire boot off and remove the spark plug to be checked, using a ratchet and spark plug socket. Install the spark plug boot back on the plug.
Grasp the spark plug boot near the wire. Keep your hand away from the electrodes of the spark plug.
Hold the spark plug base against the engine block, or some other unpainted part of the ATV that is grounded to the negative side of the battery.
Turn the ignition switch on and operate the starter for no more than 10 seconds. Observe the spark at the plug. Try a different grounding spot and make certain the plug is grounded if there is no visible spark. Persistent lack of spark or a weak, orange colored spark indicates a problem in the ignition system or the spark plug itself. A strong, blue spark with a clearly audible report indicates a good spark.
Tips & Warnings
- If you don’t get a spark, try a new spark plug. If the new plug sparks, the problem is the old plug. If the new plug also does not spark, a problem exists somewhere else in the ignition system.
- Do not operate the starter for more than 10 seconds at a time or you may damage the battery or starter system.
- Keep your hands away from the spark plug electrodes and the open end of the boot. The ignition system steps up the voltage considerably at the spark plug and can deliver a rather severe, if not dangerous, electric shock.
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