Need a little help. I just rebuilt the engine in my wifes 88 Trail Boss ES. It has a rebuilt top end and bottom. The carb was also rebuilt. For the breakin I am running a 38:1 gas to oil as I have removed the oil pump. The atv starts and idles great. The problem is when I rap the throttle it backfires through the carb. Is this a lean condition? Do I need to raise the needle ? I have the pilot screw turned out 1 1/4 turns. If I open the throttle slowly it will build up rpms. Is it not true if you open the carb real fast and it backfires it is because you get a sudden rush of air and the fuel can't keep up? Thanks for any help

 

You definitely are on the right track. A lean condition generally causes a backfire through the carb. Raising the needle (lowering the clip) causes the needle to be raised higher out of the jet that it sits in, therefore enrichening the mixture.

I wish that I could be more specific on the proper adjustments to make, but I'm not that familiar with your atv. I'm sure that others will be able to be of better help.