Does it die as you twist the throttle or after riding it a short distance? I know its seems a silly suggestion but are you turning the petcock in the correct direction? Try the twister in all of the setting positions and see if a different one fixes the problem. Keep in mind if it dies on a throttle twist it might not be fuel causing the problem.
Simply unplug the key switch you might find the electric start works too if not should start by hand of coast start every 4 wheeler I can ever remember always started this way hope that helps good luck
if the o2 sensor is still in the pipes , it is ok
if not have the adaptor fitted to the pipes and it will be ok
the sensor reports the gas composition to the ECM to adjust the air/fuel mixture
if the new pipes are pollution control compliant the adaptor should be already there
if they are not then you are achieving nothing with the different pipes but are actually decreasing fuel economy
If its a 2 stoke,"takes gas oil mix", piston in backwards,, ,,,,if its a 4 stroke "takes gas only"...rocker arms need adjusted, or cam not set in proper place during resembly "out of time". Or a. Bent valve/valves,,,in the head, valve will have to be replaced
You need to first determine whether the problem is fuel or electrical. Remove the sparkplug and pour in a small quantity of gas. Replace sparkplug and high tension lead. Crank it over. If it does start and run a bit then your problem is fuel and not electrical. If it does not fire and the sparkplug is wet, then start be replacing the sparkplug with a new one.
Sounds like it may need some carburetor work. If you've stored it without any fuel stabilizer added, mixed well, and ran through the carburetor a little, even for as little as 30 days, the fuel can break down and leave deposits on the small mixture jets inside. Spraying some carb cleaner while starting and running will sometimes loosen up those deposits, but more often than not the carb will need to be taken apart and cleaned.
Try taking a look at the starter and flywheel while attempting to start the engine. Does the small gear at the end of the starter move forward and engage the flywheel when you try to start the engine? Could it be stuck? The small gear must move forward to engage the flywheel. Keep your fingers away from the moving parts.
Your 4 wheel drive may be working, but it is a torque-sensing front
differential for reduced steering effort, that supposedly sends power to the wheel with the most traction. Many owners have found that just the opposite is true. Your problem may mean that the differential is working, but because it doesn't lock up both tires in the front and only one tire is getting all the traction you can't see it work as advertised. The link to the video is great for showing what may be happening. The front differential may be worn out and need to be fixed or it may just be that it is not working as you expected: https://www.youtube.com/watch?v=KF-iD4pmmoA