My new bike is running like crap. It spits and sputters more than a baseball player. Every time i get on it it back fires. We have Tried about 30 different spark plugs on it. We dont know what year it is. from some research we think it is a 89 quadrunner or quad racer. we dont know for sure though.

HELP!! Can someone tell me what i can do to get this thing running right. What spark plug i need to run and what gap and what i can do to help it.

 

I forgot to add that it has a aftermarket carp. dont ask what it is bc i have no clue. we havent looked into it all that much. i know it runs pretty good when you are just cruising not hammering it but when you hammer it it spit and sputters and backfires. i want it to run good. i want to be able to outrun my uncles 350 banshee.. they are both 2-stroke

 

Its too lean. You need bigger jets. If you keep running it like that, you'll blow it up!
You'll never outrun a banshee with a 250 unless there is something wrong with the banshee (or your uncle).
If you have a 250 and its 2-stroke, its a quadracer. Not quadrunner.