Friday, November 22, 2013
Motorcycle Spark Plug Specs
Knowing a spark plugs specifications is crucial to understanding how the engine operates. A spark can make an engine run well, or it can damage it with pre-ignition. If you do not use the plug with the correct rating, your car will not operate properly.
Why Plugs Need Ratings
Different spark plug lengths are compatible with cylinders of different sizes. Different engines also require plugs with different spark ratings. Depending on the engine, choosing the right plug ensures the fuel burns efficiently once the piston compresses it against the cylinder cap.
Sparks also indicate whether the engine is burning fuel properly. If the fuel is burning too lean, the spark plug tip will show a chalky white residue. If it is burning too rich, the plug will be black or oily.
Spark Specification Coding
Sparks are usually coded in four digits. The first letter is thread diameter code. This lets a user know the plug will fit right in the engine socket or not.
The second digit is a number for the heat rating (the lower the number, the hotter the plugs spark).
The third letter is a digit for the length of the plug (short or long). Smaller engines tend to use a shorter length that screws into the cylinder cap.
The fourth digit is for any special codes of manufacturing company differences and brand identifications.
Lastly, if a fifth digit exists, it represents the electrode gap measurement.
Using the Wrong Plug
While spark plugs are generally designed similarly enough that they can be used interchangeably, doing so is not a good idea. The wrong specification will mean the spark plug will run too hot or too cold and foul.
Running too hot is more serious; a hot spark plug will cause pre-ignition which makes the engine misfire and can melt a hole in a piston.
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