Situation: I have a US41 that is nelatively new and ran just great until I changed the carb. The original carb did not have a choke.

The plane will not run. If I choke it GOOD, it will start and only run at high rpm settings. It will die at or above 4000 rpm. the new carb is a Q42-52 hop up carb sold by B & B. It is exactly the same design as the stock carb except for a choke and different jetting I guess.

My engine has the black plastic spacer plate with the 180 degree channel that allows the carb to be mount either side up. I have mounted it exactly like the stock one. All holes and channels line up, good fuel flow, no air leaks I can find. It just will not start as easily as it should, and when it does start will not run below 4000-4500 rpm. When it gets down around 4000-4500 it will start to surge a little then die.

B & B has tried to help, but I'm not getting anywhere. Does anyone have any idea whats wrong. thanks