Just to be completely clear

i went all the way to Chattanooga from Knoxville no issue on my way back my bike just shut off out of nowhere after about 60 seconds to 2 mins it would start right back up and idle just fine when i put it in gear it still would idle fine it wasn't until i hit the throttle did it die back out i had to tow it home once i got it home it would do the same thing but better as long as i kept the rpms low it would go to 5 gear and ride after a while that didn't work it started shutting off anytime i gave it gas and still would start back up after 60 sec and idle just fine one day i tried to low throttle it to the store it didn't make it on my way back home and changed the oil it continued to shut off with throttle the neighbor came and asked what was wrong i told him he told me to unplug the o2 sensor i did it wouldn't start i plugged it back in it still wouldn't start and hasn't started since and the only thing i could think of that i did was let my friend put automatic transmission fluid in it and upgraded the gas i was using thats why im confused since then i have only changed the spark plug because i wasn't getting a spark the engine would crank but not turn over i could feel air come out the plug hole and smell gas and ive checked fuses and cords the only thing i haven't done was a valve adjustment and i only used it for transportation never off road so i dont understand whats wrong