William,
First of all, thanks for your patience and your suggestions. I also own a CT4-S and do not have these problems.
-What do you mean by"clear out the engine"?
-By "hear the idle drop" you mean that when you push the throttle and then let it go, the engine will be revving down slowly until it gets to idle? and once it reaches idle, it should shut down after 9 seconds or so, if you do not give it gas?
-Do you refer to 'rich in the bottom' to the LSN being too unscrewed? too out?

I'll try all your suggestions and look forward to your comments on the above. If I can't make this thing behave, I'll definitely get rid of it; I even bought a new carb thinking that was the problem -it wasn't. CEN really needs to work on this engine.
Thanks also for the air filter tip; didn't know that.
Alex