READING SPARK PLUGS

Q: Is there any place on the Internet where I can see pictures of spark plugs and learn how to read them?

 A: I don't know of such a guide so I put one together for you, of the five popular spark plug patterns for two-stroke engines.

 Heavy Carbon

This plug has heavy carbon build up. This engine had a blown crank seal on the tranny side of the crank. Tranny oil entered the crankcase and was burned in the combustion chamber. Engines like this will billow thick blue smoke out the exhaust pipe.

 

Wet Fouled

This plug is wet fouled. The spark plug's heat range is either too cold or the carb jetting is too rich.

 

Sand Glazed

This plug has a shiny appearance. The engine had a problem with air filter sealing. Sand entered through the filter and into the engine. The high combustion temperatures caused the sand to melt and form glass around the spark plug.

 

Melted Aluminum

This plug has tiny globs of aluminum packed around the insulator. The engine suffered a meltdown from ignition timing that was advanced too much. The heat could not transfer from the spark plug fast enough and the center of the piston melted causing the molten aluminum to collect on the plug.

 

Perfect Color

This is a perfect plug. The color is mocha brown so the carb jetting is optimum. The first three threads are black signifying the plug's heat range is matched to the application. There are relatively low deposits considering that this engine was run on regular pump petrol.