Is the plug wet and smells like gas? If so, it sounds like you are flooding the cylinder (with gas), and you're extinguishing the spark (flame) and the spark plug may not be re-usable at this point. This is called a fouled plug. If you have a fouled plug, and you keep trying to get the bike running, you are chasing your tail, and typically aint gonna happen. So start with a new plug.
This could be caused by a leaky float valve, allowing way too much fuel into the float bowl, and into the jets/venturi. If you dont know what this is, you need to do some basic research on this, its not complicated, and works just like your toilet in your bathroom.
There are two (3) conditions in ANY vehicle that uses a liquid gas - you are either running rich (too much gas) or running lean (not enough gas) to sustain engine performance. Right in the middle is the 3rd, and its the sweet spot that we all strive to achieve, but more often than not, we are not there, and are either rich, or lean. This is why computer controlled fuel injection is best, but I digress...
The condition of your spark plug is the best way to determine where your engine is at; wet = rich/flooded/not running. Dry = running, and a good start to diagnosis.
