I just bought a 400 big bear that will pull good at low rpms but when rpms get higher it starts to slip! I ain't sure of the oil type in it but would the bike act like this if it was not the right oil! Or is it the plates or the centrifugal clutch? Any input would be great thanks

 

There is a clutch adjustment on the crank Case and only use oil mad for wet clutches.

 

I did try the screw on the side and it went from bad to worse