This is a very low time, nearly new, 91 AC with large needle valve.

First and I think suspect, the engine will get fuel with 2 to 3 flips cold with throttle open full and glow plug detached. Fourth flip at just above idle with glow hot she's running.

When running everything is terrific only when slowly accelerating and decellerating. The problem comes when you jazz the throttle. Response is awsome but carb becomes loaded and stays that way.

One of the guys at the field with many YS engines said that the carb box gasket may need to be cut at a certain place.

Please advise.

Bob J.

I would first try screwing the regulator in about 1/2 turn, then tell me what you get.

Thanks, will do and let you know in the next few days.

Bob J.

Please let me know.

After talking with you on the phone I pulled the cowl and tightened air box bolts and a few others and figured I'd give it another try before changing any seals.

Fuel used is Magnum YS/DZ Blend (we were told it's 20%).
I also have Magnum #1 2 cycle fuel (we were told it's 25%).
Prop now is APC 14/10 balanced.

RPM peaked at 9000 and cracked it off to 8800 (about 2 clicks rich).
Needle valve is 1 turn out. Idle screw is about 1 1/2 turns out maybe more. Idle was adjusted by sound, peak was smoothest running. Either side of peak engine had slight uneveness.

The large midrange screw 1/2 to 1 turn in from flush.

It is now consistant and does not load up when quickly throttled up. Midrange is uneven not smooth, still a little rich. Engine will idle forever.

My questions:
1. Should I go to 14/8 prop to get rpm in the 9000-9500 range?
2. Midrange is uneven and still a little rich. How about if I adjust that large transition/midrange screw while the engine is at 1/2 to 3/4 throttle where it is uneven?

Thanks for your help.

Bob J.

Sounds fine with the prop you are using, no need to change.
If you fiddle with the regulator screw, shut the engine off, you don't need a trip to the emergency room. There's always the chance it is still too rich.