Now it sounds like you're having the exact same problem I was having when I had my fuel line hooked to the wrong brass tube on the carb. Low needle worked fine, high needle didn't work at all, engine died when I tried to throttle up. Does your carb have 2 tubes?

Yes my carb does have two tubes but I am 99.9% shure I have the fuel line conneted to the correct tube. The tube closest to the engine by the adjusting needles is the primer tube which I have blocked off and the barbed conector on the other side of the carb is my fuel inlet.

Both of the tubes on my carb were on the same side and I was 99.9% sure I had them hooked up right too! What model # carb are you using?

I believe my carb is a wt-349 12.5mm bore. It has a brass tube beside the adjustment needels that I am quite shure is the primer tube and a fuel fitting on the other side of the carb with a 90 degree barbed plastic fitting that I am quite shure is the fuel fitting. I can blow air through the primer fitting and I can not blow air through the barbed fuel fitting.

I found this right here on RCU, seems odd that he had several of the same carbs as yours with the same problem...

http://www.rcuniverse.com/forum/m_58...tm.htm#5818624