Size

Let us distinguish the important difference in spark plugs threaded ends. They come in four diameters and lengths. They come in nominal 14, 10, 12 and 18 millimeters diameters. Previously, there was a slight difference in thread configuration especially in different countries.

However, the international standardization of the thread forms made it uniform. These new dimensions are now being followed by motorcycle parts manufacturers.

Usual Errors

There can be lots of error in selecting the best motorcycle parts especially in the case of spark plugs. The very usual error is using 3/4-inch plugs in 1/2 -inch holes. The result of the same is horrible. When the plug threads are exposed in combustion, they become filled with deposits. Consequently, it will be hard to remove the plug without removing the hole threads.

Quite the reverse, if you use a short plug to a deep hole, the deposit will fill the hole and it will be hard to re-install the right size plug. The worst error is the use of overly-long plug. The exposed threads absorb great amount of heat from the combustion process which improve the plug-nose temperatures.

As a consequence, the side electrode functions as a glow plug. Early ignition or runaway pre-ignition causes higher combustion chamber temperatures that can destroy the engine.

Heat Range Demands

Hot plugs come with a long insular nose. They lead heat high into the plug body before it returns to the cylinder head. Short-nosed plugs, on the other hand, have shorter heat path. Consulting the spark plug manufacturers regarding the plug’s heat range can be of great help.

This may somehow clear the cobwebs at the back of your mind regarding heat range demands. Knowing which plugs are colder or hotter may be easy if you stick to the same brand however, it becomes perplexing when you change from one brand to another.

There is more to spark plugs than the three aforementioned aspects. There are still areas that we need to master like its installations, different plug configurations and maintenance work. Nonetheless, we have to be first acquainted with these three aspects.

You must know more about spark plugs to pick the best type. Another, you have to complement your choice with your bike engine’s condition. These factors are hard to acquire and do, thus, we have to instill lots facts all at once. When you get it right, you will be greatly benefited.

Charles Baldwin
20 October 2009

Charles Baldwin has been a biking enthusiast for over 50 years. He has been a motorcycle mechanic, racer and builder of custom motorcycles. He has traveled extensively by motorcycle, and if he recommends it, then you can believe that he has been there, done that, and got the T shirt!

 ↑ Back to Top