i recently realized that my quad would pull to the left, especially when i wheelied it. So i stoped and realized that my axle bearings were shot. i just got them replaced and it still pulls slightly to the left. im not sure why but my one tire is worn away more from the play in the axle before i replaced the bearings. Could this be it or do you think it may be a more serious problem?
Please respond...need to know soon!

IF your left tire is the one that is wore more, then that would make the diameter and the circumference lower then the right. Meaning that for every rotation of the axle, your left tire goes less distance the your right. This would cause your right tire to push farther ahead making it seem like it is pulling to the left.

It is also possible that your front end alignment is off, Like MINE!, and if you are on stock a-arms, like ME, then there is nothing you can do but buy new aftermarket a-arms.

I think its my tires. but if the front was out of alignment, would it still pull even with the front off the ground?

no....its more likely because of your tires are worn uneven. but even new tires arent perfectly even. it could also how you sit on the quad. if you are leaning more to one side or the other.

make sure the tire pressure is the same in both back tires for wheelies. If your bike seems to vere to the left or right...try adjusting the tire pressure to correct your direction it works! make sure you have a ultra low, accurate, good quality air pressure gauge.

the only time i have had it pull when i pull a wheelie is if one tire is in looser terrain the the other, like packed dirt and loose gravel and the edge of a trail. When i stand on the throttle the one tire in the loose gravel will get no traction, while the one in packed dirt grabs like glue. Makes the bike twist pretty quick.

But i still stand on the fact that ur tires are of different wear, and like said above, new tires wont be perfect. so check tire pressure to make those fine adjustments

Thank you all for the input. I looked at the tires today and the left tire if just slightly more worn than the right. Now that i found the problem, i don't have to worry about it because some people told me that my frame may have been bent or the swing arm could of been mis-aligned.

if your problem was in the front end, even with stock a-arms, you can align it. the tie rods are adjustable.

and always check the simple stuff first. i.e. tire wear or pressure.