I have a carb issue with my 2000, 600 grizzly. 90% of the time it runs fine. Then, it will start to run very lean and die unless I pull the choke lever out. Also, I can make the thing die or atleast stumble badly by rocking the whole thing from side to side. I have had the thing apart three times cleaning and recleaning. I rebuilt the carb the first time I cleaned it. It also like the mixture screw about 4.5 turns out. Any idea on what to check???