It seems like when the rpm drops at full throttle the smoke increases. I had this engine in a astro hog about 8 years ago and it had a surging problem back then but it did start better. But I was also using an electric starter then and starting it by hand now. This is the first time I have ran it in about 8 years but it still runs the same as I remember it. It acts like it cant hold a needle setting. Also the engine has very low usage on it. I'd say 15 to 20 flights. I have taken the carb apart and everything looks fine. I noticed the needle valve was loose so I put some fuel tubing over it. Did not help. I also ordered a prop balancer thinking maybe the fuel was foaming by extra vibration.