I have an old old Troy built horse with 5 hp tecumseh. I can start it up and it will run forever, but when I start to engage it and start tilling it shuts off. I can't understand why this happens, my understanding of a small engine is was either it runs or it doesn't. It has to be the carb, I guess. I tried all the adjustment screws whether they were adjustment screws or not. No adjusting kept the problem from continuing. I did remove the bowl screw and found the rubber gasket was flakey and part of it would come off in my hand but was still intact. Could this be the problem? Why would it not run when engine was engaged to work mode is beyond me. Thanks for any help