Try installing the air filter, but just lightly tighten the screw. Running with no filter will greatly shorten the life of your engine.
Rivets, you 'da MAN!! As I had mentioned in a previous post, I know that running an engine without the airfilter is not the best (right) way to go, but if that's what it takes for the engine to run, I was going to do it. However, I decided to apply your suggestion of not tightening the screw on the airfilter cover so much. Voila! It runs like it is supposed to. Good on 'ya, Rivets! Evidently, the air filter was being pressed into the choke butterfly and wouldn't allow it to open completely. Of course, when I'd remove the airfilter, everything looked fine. Anyway, to all the rest of us 'shade tree mechanics' out there, the problem is solved. The first time I lightly tightened the screw it was too loose and the filter cover popped open after about 10 mins of running the mower while mowing the lawn. So I tightened it a little more, but paid close attention to when the screw made contact with the cover, then went about a half turn to a full turn more and it stayed in place. Thanx to all of you for your posts and suggestions and input. I wanted to let you all know, what solved the problem, as well as the cause; just in case someone else out there is having the same issue. Take care ya'll. Volklskier