Exception to every rule!
I agree with everything that was said above, but believe it or not, being excessively rich on the Low speed needle can also lead to an engine running on. If rich on the bottom end, rpm decreases & engine will stall. To combat this, some people turn up the idle on the carby (screw it in). As you come off the throttle, the engine still has a belly full of fuel and due to the idle screw (on the carby) keeping the throttle slightly more open than usual, this causes the eingine to run on.
The solution would be to return the carby to factory settings, adjust your trim on the radio, set your gap (throttle opening) to 0.5mm with the idle screw. Then you start tuning at the top (High speed needle), then the bottom (low speed needle) for response off the line, then adjust the idle accordingly.
p.s. I was told this by the Australian 1/8th scale champion last weekend,and he also demonstrated it to me. I had the exact same problem with my N12LL3.
Im not saying that this is definately the problem with yours, but its worth a try.
Hope this solves your problem!
Last edited by Rody; 11-25-2005 at 01:13 AM.