Need help on 1998 bayou 220...not starting.?

i have a 1998 bayou 220, i had it running for a little while and then suddenly one day it would start. the electric start never worked so i always pulled started it. i found out online how to jump it by putting the screw driver between the starter relay terminals and i did that and it started right back up. i tired it the next morning and nothing happened, it would still try and turn over but it would never fully, i took the carb apart and cleaned it and then i tried to use start fluid in it but still nothing. sometimes it will backfire when trying to crank extremely loud, sounds like a gunshot, i have checked the timing and it might be a little off but im not exactly sure. any other ideas of what it might be?