ATV won't start.....Help Me

[02YamahaBigBear400]

Hey guys maybe someone can give me an idea to whats wrong. I have a bigbear 400 4x4 and 3yrs ago i was pulling a friend out of a mudhole but my bike was idling as i was trying to relocate the rope for a better pull. Well the bike shut off. Since then i haven't been able to start it. 3 yrs later, I've taken it outta storage to work on it. Just the other day i checked for spark......got that, gas......its getting that, carb and tank are cleaned out and fresh gas has been put in. It still won't fire. Every now and then I'll get a backfire or it pops my carb off the boot going to the cylinder. I haven't done a compression check but I have stuck my finger over the spark plug hole and it blows my finger off. I'm clueless to what has happened. Can some help or have any idea to what is wrong. Thanks

[yz450f rider]

try straight wiring the kill switch    was it idleing in water??

[02YamahaBigBear400]

it was out of the water on land. my friends was in mud. but the kill switch works cause if i kill it, it won't let me crank it. I'm thinking my timing or my valves. But i never had my valves knock or right now as i crank it I don't hear anything knocking around.

[bocephus300]

id say it maght of jumped a tooth in timing or the chain tension is bad.  cause its blowing the carb off, meaning its sparkink while the intake is open or partially open.

[grizzlefoshizzle]

check the parking brake out if its on it wont want to start cause of its weird

[MuddFreak77]

Its a timing issue, as was already said if its blowing the carb off its sparking while the intake valves are open.  Check the timing chain.

[MadMudder]

I agree its either a timing issue or your carb might be loose. Id check both.

[scrimmy]

^^^^^^ agree

[4fittyr]

if its a yamaha my buddies raptor wouldn't start  did a valve adjustment   not much paper thin but the intake was closing before it could fire so opened up a lil more than need .0003  on mic cause their gonna close up again  hope this helps    fired rite up