I have a 3W-240 gasoline engine with a Johnson header (M185-S) and a 36-14 prop. It has a CDI ignition and I am running superklots 2cycle oil at 40:1. Everything was bought from Cactus Aviation and I can not get a reply from them. This was a barely used setup I got from a friend and it has only an hour or two on it. I bought it knowing that it had problems but I thought that since it was new I could easily fix it. The exhaust pipes were cut down three inches on each pipe so that they would be flush with the cowling. I didn’t cut the pipes they came that way. The problem is that the engine runs like crap and has a hard time running for a full ten minute flight. I have replaced the spark plugs, cleaned out the carb and put the engine on a test stand and have a strong 6volt power supply running the CDI’s and they are 6volt CDI’s. There is a strong spark but one other weird thing is that when I adjust the high speed and low speed air/fuel mixer screws it takes about 2 seconds before the engine changes to my adjustments. I know that these engines don’t change imminently but I think that it shouldn’t take that long. The adjustment screws are very sensitive when I am getting at the top of the adjustment where you are leaning it out. The engine will either die or run rich and rough. I am just getting into the very large aircraft I have been flying glow fuel airplanes and helicopters for a long time and also small 30cc-50cc gasoline airplanes. I know that the exhaust system can make or brake an engine so is there a better exhaust that will make it run better but more importantly give me more power. The CDI is a dual setup with two spark plugs per piston and each spark plug is connected to one on the two CDI ignitions so that if one spark plug or CDI fails the engine will still run. Any ideas or tricks would be very helpful and also around what rpm should the engine be running at full power on a test stand? Thanks in advance and I will keep updating this as I keep trying different things so that this might also help other people with engine problems. Thanks again Bryan.