PROMAG, I did check the valve adjustment and it was ok at .004 inch. Both engines perform perfectly well at all levels except the poor idle.

Inorris, I agree that it does seem like a low end mixture problem. Actually I get a substantial drop in RPM on these motors if it is on the lean side as well as on the rich side. If I get it right on the money, it doesn't drop off. I verify my low end mixture also by checking its quick transition from idle to full throttle. It has a nice transition. As far as the exact RPM at idle, I haven't checked it with a tach. Both engines used to idle with the plane just sitting there. Seemed as if I could count the RPM. It would just putt putt putt for 30-60 seconds or so. Now I have to have on a good pair of Nike to keep up with it taxiing out to the runway or it will die. Well, it's noticeably worse anyway.

I'd also consider tightening the wheels more with the fuel tubing on the axles but it is disappointing to have to just compensate for whatever this engine problem is. I wouldn't mind doing so if I identified some kind of costly problem with it but I'm thinking/hoping it was something minor I could resolve.

Anyway thanks again guys for your feedback.