Hi Dave,

Ran another 1.5 tanks (16 oz tank) of fuel through my new YS1.10 tonight with the engine mounted in my Funtana 90 and the cowl off. This makes a total of 3 tanks of fuel through this engine.

I did as you suggested, and turned the regulator adjustment screw in 1/4 turn at a time. I experimented only with regulator screw settings that were clockwise (lean) of the regulator screw being flush with the regulator housing. I would make the regulator adjustment, take it wide open and set the high end needle about 300 RPM down from peak (plenty of smoke), set the idle screw as best I could, then test transients and midrange performance. In every case, the top end and transient performance were great, the idle was so-so, and the engine would never run properly from just above idle to about 3/4 throttle. If you tried to hold a constant speed in that range, the engine would start hunting, then die. Hooking the glow starter up made a substantial improvement to this midrange problem. Even with the regulator screwed all the way clockwise, transient performance was still great? Doesn't make sense to me.

Tomorrow I'm going to reset everything back to factory recommended initial settings, then go from there.

Any other suggestions?

This thing pulls like a horse (16x6 APC @ 9200 RPM at 4700 feet on 20/20!) and has great throttle response. I can't wait to get this mid-range problem fixed.