RE: ASP FS61 midrange problems
w8ye, I'm no engine expert, but I think I have tuned the engine like you describe. And I really appreciate your help. When I tried to find the correct setting for the low speed needle, I leaned it until it wouldn't accelerate when I hit the throttle, and then I richened it by a few degrees. Just enough to make it respond to the throttle stick. Even with both needles at their leanest possible setting, the midrange is very rich (rpm decreasing, vibration and lots of smoke). If I advance the throttle slowly from idle to full, it sounds clean at idle, then gradually rougher, then at about 2/3 throttle it jumps up to a much higher rpm and sounds clean again. I have several other engines and tune them the same way, and they all work well (except this one).
The strange thing is that the engine behaves the same with two different carbs. At first I thought the original carb was faulty and got a new one from the hobby shop. Then I started the engine with the new carb and saw the exact same problem. What is the chance of getting two faulty carbs in a row? It sounds strange to me...