You Tower Engine users, I am with you too. Have had mine for three years and have not touched the needle valve at all. It runs great and I have worn out 3 Contenders with it. That being said, I now have a problem. Sat. I came down a little hard on the spinner, but did not break the prop. Now it will not go to TDC without binding. I pulled the back plate off, no gauling. Pull the carb off, no sign of unusual wear on the crank shaft. Pulled the head and when I tried to pull it through the innerliner was forced up before the piston would go to TDC. The piston is black from so many runs, but I don't think this would affect it that much. Any clues to what de problem be or a solution. I know it is a pretty inexpensive engine and I have an OS to replace it, but it was for my beater plane and I would like to save it if I can. Thanks men.