i just rebuilt a carb. on a 94 yamaha timberwolf...it will sit and idle...but when i go to give it gas it sputters and backfires and quits but then i can start it right back up and it will sit and idle untill i try to give it gas again,can someone help me    

sounds like it is running rich, but however have you inspected the diaphram in the top of the carb for wear or holes?

this could cause it as well.

if so and there no holes or defects in the diaphram.
it could be as simple as retuning the fuel/air mixture screw.

the first step is to remove the airbox lid see if it runs any better or any worse.
if it runs better then it is running rich, if it is running worse, then it is too lean.

turning the fuel/air mixture screw to the left will add more fuel to the mix.
while turning it to the right will decrease the amount of fuel in the mix.

mark the screw and the carburetor so that you know where it was originally and make your adjustments in 1/4 turn increments. letting it run for a few minutes in between.
keep up with how many 1/4 turns you make