I believe it's gas. It doesn't smoke much at all when it runs...what little there is appears black when first starting. Last year replacing the air filter seemed to help. Since then I've cleaned it regularly. It does run better with it off...are they all this touchy with the air filter? First 4 wheeler we've owned. When I tried starting it with the air cleaner off, some gas came out in the air cleaner compartment.
I'm not sure what the connection would be between valve clearance and carb issues, but have seen that conversation elsewhere on here?
There is a link on here for free service manuals, but they only go back to 2003 for my 300. Is that close enough for things like valve clearance?
Part of me just wants to throw in the towel and buy a new carb...