I took a new LO206 out to the track yesterday and had a heck of a time trying to get the most out of it. Take off was fine, midrange was fine….then it would sputter before getting max rpms. We tried moving the needle all around and ended up getting the best response from clip on the needle being at the bottom, the idle screw turned all the way right, and the air mix screw almost all the way left. It seems like it is still running rich and with those adjustments…there is no idle.
Agree with Tony on this but would also take the carb off and apart for a good cleaning / inspection. There is not a lot to them. Guessing that you are using a good quality fuel filter and that the tank and likes were sanitary ? We use a ultrasonic cleaner on carbs after every outing to ensure that they are clean and remain clean. Not to mention the fact that pump fuel can often lead to problems.. If you continue to have problems, give us a shout..
Check your throttle cable for the idle issue. Some cable ends are to long or to big and don’t set in the slide recess. I believe this puts things in a bind and wont let the slide return to its lowest point to where you can get an idle. Mine was so bad, the idle screw had “No” effect on idle adjustment. If you don’t have it already, Briggs has a carb tuning guide on there web site. Follow their guide and you should be ok. http://www.briggsandstratton.com/engines-racing/~/media/Racing/carbtuningguide.pdf
I have found two reasons why it won’t idle. One is that the needle clip set at the bottom setting. Try the third down from the top. The other reason is the air mixture jet is plugged. Take a strand from copper wire .010 thick and run it threw the jet to clean it. (don’t enlarge the jet, tech item) . This was the cause on two different engines. Good luck.