how old is your fuel?

i am doubting that it is a piston/sleeve problem, since that usually occurs gradually not immediatly. u would have seen that coming, unless u did something drastic to the engine, such as over rev it, or over lean it.

do u know anyone with a starter box? it would help, rather than yanking on the cord 1000 times.

u said that u have checked the new plug u put in? sometimes its the glow starter thats bad. check to make sure the plug is glowing brightly.

after that - make sure u can answer yes to the following questions:

my glow plug glows bright and hot
good, new fuel is getting to the carb, i can see it.
at idle, my carb is open about 1mm
my needle settings are correct.

thats it. if u have fuel, fire, air, compression, and the right fuel/air mixture - it WILL start.