If there's good spark...
Remove the airfilter and spray fuel in carb while cranking. If starts and runs for a bit, it's your fuel delivery.
Dump the tank, blow out the lines, put a $10 carb kit in (clean the carb while installing). Then get some fresh premium fuel and 9x out of 10 the BS will run for another 15 yrs.
....then use fuel stabilizer in every tank and you'll avoid many future probs. Also avoid modifying the fuel system unless you know what you're doing. They run the way the factory made them and often don't after some "handiman" remedies.
HD