Just got this atv for free from a buddy. Just curious about a shifter I don’t know much about atvs, motorcycles are my strong suit. Missing a piece as seen in the picture but not sure what goes there and how to shift? Any and all info would be great and appreciated

 

That is just a hole for checking the top dead centre mark on the flywheel, should have a blanking plug in it. As it hasn't a gear lever it will be "rev and go."