95 425 Mag Fuel is in my oil

Hey Guys and Gals, I’m new to the forum but old to Polaris. Can someone out there give me some help? I have a 1995 425 Mag 4X4. I bought it new. About 1 year ago I noticed my engine oil smelled like Gas. I took to my dealer and he replaced the petcock and rebuilt the carb. Well a few months ago I noticed it doing it again. A friend says the petcock may be bad but I didn’t think leaving the fuel on would cause that. Any suggestions?

Thanks