Since we no longer have parts for this engine other than the diaphragm (same as the YS 45), you are pretty much on your own as far as parts issues go.

You may be a little light on nitro in the fuel, they ran better on 20%. Most guys used an OS #8 plug. It sounds too rich at the top end. High speed needle should be at about 1.5 turns open. If you are further out than that it is far too rich.

The regulator starting point is top of the adjusting screw flush with the top edge of the casting it sets in. The regulator controls the transition from low to high and has a slight effect on the idle. Clockwise leans the transition. Work in 1/4 turn stages on the reg screw.

Idle mixture is essentially fixed and only controlled with butterfly opening.

Good Luck