I have a Bolens ST160 Hydro Suburban Tractor ride on mower, with a B&S 16hp engine, model no. 402707. I need to know the air gap measurement between the coil and the rotating fin housing (I"m not sure of the name of the spinning top part on the motor.) I have been told it is 10 thou, and again 20 thou. That"s a big difference. Who is right?, or are they both wrong. I would really appreciate someone"s help with this problem.