Bought a 01 Grizzly and was going over it. The exhaust was opened up at the rear (spark arrester gone) so I made one to replace it. I don’t like it that loud. Any way I noticed that it was a little rich after that, black smoke and it would seem to load up at idle. It would also leak gas a little if you didn’t shut the fuel off when you would cut the engine off. I decided to check the carb and it had a 145 jet in it. I think the stock one showed to be a 143.8.The leaking fuel was a bad O-ring at the needle valve seat. Weird float system in these things. The guy I bought it from said it had a weisco piston in it and he had the head "ported and polished". I am not sure of either.Should a 145 jet run O.K.? Also I have noticed a little bit of chain noise in her and the chain tensioner is all the way extended. Are the 600’s bad for jumpingor breaking the chain or can I wait till off season to put one in it. By the way, when is off season?