The causes of spark plug fouling are the same for all vehicles.
Spark plugs foul when something interferes with or blocks the firing process. This normally occurs when a foreign substance saturates or clogs the firing end of the spark plug, causing a short or misfire. In 1999, Honda introduced the Four Trax 400EX all-terrain vehicle, also known as the TRX400EX. This high-performance ATV features a high-performance, 397 cubic-centimeter, four-stroke engine that is air cooled. Since the 400EX is a large, single-cylinder engine with one carburetor, there are only a few potential causes for fouled spark plugs.
Oil Fouling
Excessive oil on spark plugs is a common cause of spark plug fouling. Plugs fouled in this manner are soaked by oil forced into the combustion chamber. Oil fouling is often caused by worn piston rings or cylinder walls. Excessive clearance in the valve stems is another cause of oil fouling.
Carbon Fouling
Carbon fouling is identified by soft carbon build up on the spark plug's firing end. Causes of carbon fouling include faulty ignition wires, a weak spark and an air/fuel mixture that is too rich. The improper mixture is sometimes caused by a dirty air filter.
Foreign Object Fouling
Types of foreign-object fouling include gap bridging, mechanical damage and splash fouling. Small objects in the engine can cause mechanical damage to a spark plug's firing end. Multiple spark plugs are sometimes damaged in this fashion as small objects can travel from cylinder to cylinder through valve overlap. Splash fouling and gap bridging are commonly caused by loosened cylinder and piston carbon deposits. In the case of gap bridging, deposits lodge at the spark plug gap, shorting out the plug. Neglecting tune ups is a common cause of splash fouling.
Overheating
Spark plugs are often fouled by overheating. This type of fouling can be identified by white or gray buildup on the firing end. This buildup often has a blistered appearance and causes the firing end to wear out quicker than normal. Causes of overheating include an over-advanced ignition timing, a lean air/fuel mixture or an engine that is not cooling properly.
Related Posts:
The Causes Of Carbon Fouled Spark Plugs
Spark plugs become carbon fouled when they have sooty carbon build up.Carbon fouling is one of the potential fouling problems that happens to spark plugs. According to NGK Spark Plugs, when the in...
Why Is Oil Leaking Into Spark Plugs On My 94 Honda Accord
Older Hondas are notorious for developing oil leaks in the spark plug wells and inside the cylinder. Honda placed the Accord's spark plugs where the plugs have the optimal effect within the combus...
What Would Cause Oil To Get On Spark Plugs
Oil on the ceramic portion of the spark plug is from an external source. If the oil is on the electrode only, there is an internal problem. This must be located not only to stop the leak, but to p...
