Carb should be a 44. That's the common carb to use.
Did you check pop off ? 2 turns out on most mixtures screw is high and needs rejetting or pop off adjusted. How is full throttle ? That is what the high speed screw affects. Inaccurate pop off can contribute to a lean or rich condition on start up, at idle, and off idle acceleration. Ideally the butterflies should be open appx .030-.040 at idle.
What aftermarket parts does the ski have ? what compression ?
Both screws at 1 turn out should be a good starting point.
decent starting point for jetting a stock setup would be 100-105 pilot, 130-145 main, 2.0 n/s at 20psi pop off (black spring).
Low speed screw handles starting and idle quality, pop off starting, off idle acceleration and some of first 1/4 throttle. Low speed jet up to 1/4 throttle. High speed jet up to 3/4 throttle. High speed screw 3/4 to full throttle. Do not use the mixture screws to adjust idle speed. The best low speed mixture setting is highest smooth idle. If idle rpm goes to high, use the idle screw to drop it, and readjust the mixture screws until a smooth idle at designated rpm is achieved. Shut it off, wait 10 min, and start it back up. Should fire off almost instantly, hot or cold.
Pop off also affects starting and idle. Pop off can be somewhat compensated for with changes in low speed jets, ie low pop off would take a smaller jet to lean it out.