It could be water forming in the fuel tank caused of condensation get a can of SeaFoam from any Auto Parts Store and most local WalMart SuperCenters cost is about $7.00 , it's been on the market since 1942 and still carries a Satisfaction or you money back Guarantee ; not many products offer this kind of Guarantee over the last 20 yrs. in the field of Small Engine Service and Repair i've never found a product that does work as good !

And it has a water drying agent , upper cyclinder lube , it will help keep the entire fuel system clean and also cleans the combustion chamber of excess carbon depots ; i highly reccomend this product as it has worked great for me and it has a fuel preservitive in it as well one 16 oz. can will treat up to 25 gallons of fuel !

And it works with both 2 and 4 strokes gassoline and Diesel fuel , and another thing i always top off my tank after every ride this helps keep condensation from turning into water ; Good Luck and welcome to the forums !.......

 

I have worked on 2 of these with the same problem, installed larger main jet, moved needle up a notch and turned air -fuel screw out to 2.5 turns, cured them, the 600 came out way to lean from the factory. Sea foam is an exellent product, I use it in all my vehicles.

 

I'm trying a dyno jet kit. Smaller needle & main jet & the pilot screw out three turns. I'm not sure about the smaller main but the needle is consideribly smaller in diameter.

 

I had the same issue with my 04 600. They are too lean jetted from the factory. I put 1475 pilot jet and a 1625 main jet. set idol at 1100 RPM. set pilot screw 2.5 turns. Your problems are gone. Make sure the Carb adapter t the head (rubber) does not have any cracks. They are hard to see. Take it off an flex it they crack a the shoulder where the carb is clamped. By the way the machine will run better in warm weather as well.