I seem to be having some troubles with the Evolution engine on my Alpha 40 (RTF). First, you all should know the modifications I've done incase it makes a difference. My trainer wanted more leway on the needle adjustments, so I removed the set pins from both the high and low speed needle valves, I also removed the flywheel from the prop driver so I could run a two bladed prop/hub.

Now for my problem. When it's at max throttle everything is great. When you pinch the fuel line, it increases in RPM slightly and everything sounds good The problem is, it sometimes has trouble getting up to high speed when it's been at idle for a little while. The guys at the field are saying that it "loads up" too much. After I taxi it out on the runway and try to apply full throttle, it will stumble and struggle to get to max RPM. It does the same thing if I make a slow speed pass over the runway and then apply full throttle. It takes forever for it to get there. It's definitely making take-offs a little scarier than they need to be.

We messed around with it a bit at the field, and according to my manual my problem indicates that the low-speed needle valve is too rich. However, we tried leaning it all the way out at the field (all the way clockwise) and it still has the problem. When the plane is on the stand, it sounds like it's idleling fine, and if you continually rev it, the engine seems to do fine. It's only when I have it at low RPM for a while that this problem occurs.

Ideas on what to try next?