I have a 1970 18 hp version of this motor. It is my "daily driver". I agree that they do not idle as well as the older versions with twin needles and the other crankcase bypass system etc. I have found that mine runs "best" with the needle way out at least 1.5 turns but probably more. It runs very rich and smokes like a chimney but it gets me through the no wake zones without stalling and idles very slow.

A slight lag coming out of the hole but it goes through it quickly because lets face it I usually run 3/4 to wide open or idle.

Mine has great top end speed. I do have the little screen but no air box on mine. Also has the annoying packing that is rubber with the tang for the needle which I find to be less effective than the older cork and compression type.

Good luck