So I recently just pick my dad up a 1988 quad runner 250 awd the bike runs but it's getting way to much fuel backfiring will not idle it self down with idle screw carb has be completely redone I'm at a loss can anyone here help thanks a lot

 

So...if you are confident the carb is good to go...things get uglier from hear as I believe that quad is a thumper...and an almost 30y old thumper to boot. I've seen ignitions do crazy things as they die...so check the spark and ensure it's strong & constant when you crank the motor. After that...it's time to look at timing...some have timing ports to view others require more work...if you don't know the service history the timing chain, cam, lifters, valves could all need servicing...unfortunately, the thumper intake system is far more complex than a 2-stroke...