For a two-stroke engine, having a new spark plug is incredibly important. Therefore, you should check your plug frequently.
By “reading” the color of the spark plug, you can tell a lot about how the engine is running. The top of a new spark plug is covered in white ceramic insulation. If your motor is working perfectly, then this part of the plug will soon turn a tan color. If your plug is gray or white, then you know your motor is running too thin and you need to take steps to prevent motor damage. First, clean your fuel system, looking for any blockages. Dirt on the carb can make the bike run lean. Check your fuel mixture to see if you are mixing the oil and fuel in the correct proportions (50 parts fuel to 1 part oil). There are many factors that can make a well-performing oil-fuel mixture less than ideal. The brand of gas and oil, as well as the density of the air, can affect the performance of the mixture.
The lean condition can also be caused by fresh air entering the engine somewhere where it shouldn’t. So you should look for loose intake manifold bolts, carburetor mount leaks, bad gaskets, and leaking crankshaft seals. You may also need to switch to a larger carburetor.
If your spark plug is black or oily, that means the engine is running too rich and not burning fuel properly. This problem can be caused by too much oil in the fuel-oil mixture and / or having a faulty spark plug that is failing. First, you need to find out if the spark plug is the problem. To do this, touch the electrode end of the plug to the motor while pulling the starter motor. If the resulting sparks are blue, then you know you have a fully functional plug. Install the plug and run the bike for a few minutes. Then stop the bike, remove the spark plug and look at it. If the plug is dark and oily, then you know that the problem is not your plug. You need to check your oil and fuel mixture. If your bike’s motor wobbles, sounds stuck, or doesn’t work clearly, you may want to get a smaller carb jet.
While you should regularly inspect your spark plug, it is essential to check your spark plug after any type of engine modification to make sure the engine is not running too thin. For standard use, NGK B7HS Short Thread Caps and B9ES Long Thread Caps are recommended. For use in competition, NGK B7HS-10 short screw caps and NGK BR9EIX long screw caps are recommended.
Check your coil first to see if you have a healthy spark. Use a new plug and ground the motor electrode while pulling the starter motor; the spark should be a healthy blue. If so, install the new plug and run the bike normally for a few minutes, remove the new plug and “read” it. If it still appears blackened or oily, the problem is elsewhere. A hotter plug is not recommended – make sure the fuel mixture is correct and consider a smaller jet only if the bike stumbles or sounds “snotty” and does not run smoothly. Using your bike too rich won’t hurt it, but too thin is never good. A little dirt on your carb could make it thin, and you wouldn’t even know why your bike runs so good and sharp until it seizes.