A youtube to watch at the bottom address or link. Notice in the video he will mention idling is a problem and I think he left it a little high for that reason.

1. Have you tried leaving yours a little high with the linkage screw vs mixture screw?

2. Are you saying you are not getting any changes when turning the idle mixture screw?

3. Have you checked to see if âÂÂAllâ your fuel lined are tight tight? Checked Spark arrest screen?

4. Will the primer bulb get hard and give good action X fuel movement when priming?

5. I fought that model or close for 3 yrs for fun when I had time.

6. The problem was opposite to yours. It started easy, idled but would die if you tried to run above idle.

7. Detecting the primer bulb was not sealed good, adding an o-ring for added pressure gave me high speed but a poor working idle.

http://www.youtube.com/watch?v=ghPFbpasx_0

Here is a link that might be useful: Youtube info