RC Showcase has the best, easiest gas tuning directions I've seen. And they actually work. Just remember that gas engines are different than glow. Glow...you set the high needle first, and then come back and set the idle/low end needle. Gas is the opposite. Set the low end needle first, since it affects the high end. After the low end is happy, then go back and set the high end.

Here's the link

[link=http://rcshowcase.com/html/faq.html#I%27m%20new%20to%20gas%20engines,%20how%2 0does%20one%20go%20about%20adjusting%20the%20carbu retor?]Adjusting gas carbs[/link]