your needle valve is just like any other screw...rightie tightie or lean...lefty loosey or richen...so now that you have run a few tanks through the engine, try this...go to full power and lean out the mixture by tightening the needle valve...you will hear the engine getting faster..it will eventually peak as you continue to lean it out and start to slow back down..stop right there now richen it back up until it's back to peak RPM stop.... now richen the needle valve 1/4 turn...
alan gave the best advice find a club that will help you....