Atv engine sounds like the idle is going up and down

Well first off if you have a problem right off of idle then you have a pilot jet issue.if it stumbles after a quick blip of the throttle then it's too lean.if you can adjust the air screw or the fuel screw on the side of the carb then do so until absolutely no hesitation after a quick throttle blip.if you can't adjust enough to fix the issue and depending on which screw you have you need to either install a bigger pilot jet or a smaller one.as far as a fuel leak verify the leak location.if it's coming out from the over flow tube the the float is set too high or the float needle and seat need to be checked out for a sticking open problem.if the float needle is the cause you will need to replace the needle and seat