The sooner you put a Mikuni on it, the sooner you will find happiness. Those old pumper carbs almost killed the sport of snowmobiling. If you can arrange a still-air box (silencer box) on the intake, so much the better. Find a carb made for a KAW 440 engine and the jetting will be close. When tuning, start off a little rich on the main jet and then carefully lean it out if you need to. Watch your spark plugs carefully while doing this. A little rich is always better than a little lean...Good Luck!