Why does my 350 yamaha atv want to turn of?

it coughs, sputters, struggles then it dies and most of the time it wont even turn on! weve already checked the spark plugs but it only seems to get a bit of spark sometimes. does anybody know what might be wrong?|||First this may sound stupid but see if your gas is turned on, after that if it isn't the spark plugs, then see if it is actually receiving gas, check your carburetor, you may need to rebuild it, you can also check your battery and see if it giving off power/holding a charge|||well there's 2 different ways... 1 is to just take the spark plug out and put your finger over the spark plug hole and turn the motor over and if it blows your finger off the hole then you know you have some compression but normally if it wont blow your finger off its not gonna run at all. second is to use a compression tester they can be bought at any auto parts store and will have instructions with it. it looks like this|||If it "only seems to get a bit of spark", install new spark plugs.