A question or two for you,

Why did you lean out the low end?
WHY did you lean out the high end?
WHY do you think the transition from low rpm to higher RPM changed after you leaned out the needles?
WHAT made you believe that the engine was rich with the cowl off?
After making your adjustment, WHY did you put the cowl on?


To me, you made TOO many adjustments all at once. When you think you have a problem, it is best to do one thing at a time. Yes sometimes it does take a combination of things to get to optimum, but you will see changes for the better or worse as you change just one thing. For the fact that this is a new engine, I would run it SLIGHTLY rich for a while anyway. You said it was rich....did you come to this solution with a tach and adjusting the needles or by the color of the plug? They way you need to set it up is to adjust the low end first for a decent idle, then adjust the high end for peak rpm, then check/adjust the low end again, then check/adjust the high end, then the low end, then the high end and so on until you have gotten optimum at both ends. While youare making these high and low adjustments, you NEED to check the transition. Once you have EVERYTHING set, SLIGHTLY richen the high end and check once again for good idle, transition and a good high end. After running the engine a bit, you can check the condition of the engine by the color of the plug. A black elctrode= too rich, a white electrode=too lean, a TAN electrode is just about perfect.

Ask yourself WHY DO I NEED TO ADJUST THE LOW/HIGH NEEDLE before you do it. If you can come up with a logical reason, then you are probably on the right track. Temps look OK.

Good luck