You shouldn't have to. If you stand on the left of the bike and look over the seat, with your head against the tank, you can just see the edge of the stud that it screws onto. Hold the end of the extended nut in your left hand, use the middle finger of your right hand to slide under the magneto, from the back, and guide the end of the nut onto the stud whilst maintaining your eyeline on the stud as mentioned before.