Scratches and scuffing below the carb indicates a poorly prepared air filter and/or a poorly fitted air filter system to the carburetor. It’s imperative to have a tightly ziptied filter neck and a properly oiled filter. The stickier the oil the better. It must be well saturated and well distributed. If there was any dirt behind the front bearing seal, replace the bearing. Off-road engines - in my opinion - should never have their bearings cleaned if dirty. They should be replaced.