How to Troubleshoot a Snapper Riding Lawn Mower

Ensure there is gas in your Snapper riding lawn mower if it is refusing to start. Fill the tank and try to start it again. If the gas in the tank has sat for a season, drain the tank and fill it with fresh gas.

Remove the cover over the Snapper riding lawn mower's engine if the mower continues to refuse to start.

Disconnect the wires from the spark plugs. Follow the trail of the plug wires further back into the engine assembly, where they run to the magnetic coil.

Locate the thin grounding wire that lies beside the magnetic coil. This connects to a plug, as well. Disconnect it in order to test the magnetic coil.

Attach an old spark plug to one of the Snapper riding lawn mower's plug wires for testing. Try to turn on the mower and watch for any sparks around the attached spark plug. If these sparks are yellow or orange instead of blue or white, you will need to replace the magnetic coil, as it is becoming too old and worn to run properly. Only the manufacturer can perform this replacement.

Check the Snapper riding lawn mower's air gap if there are no sparks produced at all. The air gap is the gap that exists between the magnetic coil and the flywheel behind it. This gap should be between 0.010 and 0.015 inches. Measure the gap, or use a playing card or business card as a guide. The air gap should not be wider than the edge of the card.

Use a wrench to loosen the magnetic coil so that you may adjust the air gap. Apply pressure to the outside of the flywheel and the magnetic coil to incrementally adjust the gap.

Remeasure the air gap to ensure it falls within the size guidelines, then retighten the coil with your wrench.

Attempt to run the Snapper riding lawn mower again, looking at the spare spark plug you applied to the plug wire earlier. Blue-white sparks should now appear. Remove the spare plug and replace the plug wire on the mower's spark plug, then reset the engine cover.