New to the World of Carbs

[300exman]

I searched past forums cause my wheeler is back firering alot when i let off the throttle. I'm reading that my wheeler is too lean but some say its the main and some say its the piolt and others say its the needle. Which is it? I have a 300ex bored .60 over with an 11:1 wiesco piston, dg pipe, k&n filter, and outware airbox lid. The guy I bought it from said he had re-jetted it for the dg and the k&n but since then I have bored it out and put on the airbox lid. :confused: I have no clue what to do thats where you guys come in:confused:. Please Help!!
Oh yeah I live in wisconsin and its in the 70's low 80's.

[cals400ex]

there is a good chance the pilot jet wasn't changed. many people go up to a 40 or 42 pilot jet. what you can try first is to turn the fuel screw on the bottom of the carb counterclockwise and see if the problem diminishes.

[wilkin250r]

Ok, look. I posted the information once and you obviously didn't look at it close enough. Give a little more information and we can help diagnose the problem.

Your pilot jet and mixture screw control your fuel/air mixture from idle to about 1/4 throttle. Your main jet really isn't active in this region at all.

Your needle will control your mixture from about 1/4 throttle to 3/4 throttle.

Your main jet size will control your mixture at 3/4 to full throttle.

Take those three statements, and combine them with the fact that backfiring means lean.

So, now you can do your own troubleshooting. Are you letting off the throttle all the way? If so, then the problem is the pilot jet and mixture screw.

Are you letting off the throttle to half throttle, not letting the throttle close all the way? If so, then the problem is your needle.

Are you just letting off the throttle a tiny bit? Full throttle to 3/4 throttle? Then the problem is your main jet.