Is your quad burning oil? From what I've seen and heard, these engines like to burn oil, especially at startup. Maybe you should try parking your quad on a clean piece of cardboard overnight and see if there's any oil marks the next morning.
When you out riding next time if you're by yourself, take a look behind you while accelerating to see if there's any faint puffs of blue smoke coming out the exhaust. If you can, have a friend ride behind you and keep an eye on the exhaust.
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