A friend of mine is having trouble with his John Deer Gator. The problem is the rear spark plug is getting fouled and it is backfiring. The dealer is running out of ideas. The plugs have been re-gapped and replced the jets. Anyone else have any ideas

 

maybe the rings are bad. that would cause that plug to foul.

Hope this helps

 

Try putting dielectric grease in the spark plug boot. It is possible that moisture is getting in there, causing weak spark, which is fouling the plug. Also check the plug wire. These suggestions are kind of like grasping at straws, but just might work.

 

Timing could be off.

Just a guess!!

 

Check the pulser coils. There are two located next to the flywheel and are connected to the ignition module. To perform the test you need a multimeter set to AC voltage and the plug wires grounded and the engine cranking. At the plug connection from the ignition module check the voltage between the BLUE/WHITE and PINK wire, then GREEN/WHITE and YELLOW wire, voltage should be between 0.1-1.0 VAC. If voltage is not normal check connections. Switch mutimeter to OHMS and check resistance, reading should be 85-270 ohms if not normal replace coils. Pulser coils part number is AM105573. If all is normal check the ignition module with a test light. At connection check WHITE then BLACK/YELLOW leads, test results should be a rapid flashing light. If not replace module. Remember to perform both tests with someone cranking the engine.