could you have missed the timing mark when reassembling it , did you check the connecting rod to see if it was bent , did you lap the valves or at least checked them for leakage , did you get an after market carb ( which is ok in my book ) ,but have seen after market carbs that are not really for the atv it is listed for , just a universal carb ------------- I think I would start with checking the timing then a compression test
As everybody told me, you need to eliminate every possibility one thing at a time.
Carb, is it genuine, set pilot to factory, make sure main clip is in centre.
Timing, take your time, turn it over a few times then check again.
Spark plug gap, set it, it should be close if new but set it anyway.
Don't get buying and replacing things until you've checked everything that could be a simple fix, you'll just waste your dollars.