For a two-stroke engine, having a fresh spark plug is incredibly important. So you should check your plug often.
There is no direct relationship between the spark plug heat range and the spark voltage.
Each spark plug is manufactured with its own predetermined and specific heat range.
By “reading” the color of the plug you can tell a lot of things about how the engine is running. If your plug is grey or white, than you know that your engine is running too lean and you need to take steps to prevent engine damage. Dirt in your carb can cause the bike to run lean.
This selection must be precise:
Today, Professional Mechanics, Do-It-Yourselfers, and Spark Plug Vendors have Application Charts available in Spark Plug or Auto Part Catalogues as a guideline to identify the adequate spark plugs for a vehicle, whether as printed material or modern computerized version. Such application charts only indicate the adequate spark plugs for vehicles under standard operating conditions.
Users are therefore quite familiarized to the idea that is enough to follow the catalogues suggestions, however, during the useful life of a vehicle many different conditions that affect engine performance may occur, as for example:
o Different driving habits,
o Different traffic conditions,
o Different load conditions,
o Different engine’s maintenance,
o Different fuel quality,
o Different weather conditions,
So you should look for loose intake manifold bolts, leaks in the carburetor mounting, faulty gaskets and leaks in the crank seals.
o Use of LPG or of Propane gas as fuel.
And when such different conditions do occur, vehicles no longer operate under standard conditions, and the heat range of the stock spark plugs stop being the adequate for this particular conditions, being done necessary to install spark plugs with a Heat Range different from the original stock suggested in the catalogues by the manufacturers, and therefore catalogue Application Charts can not continue indicating which one is the spark plug that must be installed in a vehicle to best match each one of these conditions or the different combinations thereof.
When this problem exists, the installed spark plug shows unburned fuel. Then the spark plug appearance looks similarly to a reach mixture.
If your spark plug is black or oily than that means the engine is running too rich and is not properly combusting fuel. First, you should figure out if the spark plug is the problem. If the sparks that result are blue, then you know you have a fully functioning plug. Install the plug and run the bike for a few minutes. If the plug is dark and oily, then you know that the problem is not your plug. You should check your oil and fuel mixture. If the bike’s engine stumbles, sounds clogged up or doesn’t run clear than you might want to get a smaller carburetor jet.
And if the stock spark plug heat range results hotter than necessary due to the real operating conditions, the engine would overheat and the installed spark plugs looks with overheating, similarly to a lean mixture.
Be aware that never! Never a high performance modified engine, can continue using the stock spark plug, because more power is more energy, and more energy always is more heat.
I also recommend that you learn more essays dealing with NGK Sparkplug and Splitfire Sparkplugs.
