Well, that's cutting corners
Throwing a lot of money to a probaly easy problem.
If ther is a spark, although weak, engine should start. You have a spark, so suspecting the ignition is not obvious. Before dishing out a large amount of whatever currency first check the obvious things, and make sure it is indeed the alternator. There's alos a CDI, and the coil, and the wiring ...
Fuel: are you sure enough fuel is arriving in the carb? Unscrew the drain plug, if loads are coming out (taps open :-)), you are ok. If, not find the cause.
Carb float stuck makinh mix too rich?
Check / replace spark plug, how does it look?