You want the arm to be slightly above the channel. You have to bend the arm. if the arm is too low it will restrict fuel flow. Set the arm first then do the pop off.
Pop off, low pop will not hurt you, pop that is too high will restrict fuel flow. If you find you’re sluggish coming off of tight turns and can’t seem to dial it out with the needles you would try a higher pop off.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience