Many people are confused about the sizes of the NU50 Petcock and so I took out the petcock on my 1983 junker and measured everything. It uses a 22mm wrench (O.D. nut) to remove it, and it has 14 x 1.50 mm threads. I also checked my 1983 NC 50 2-speed and it was the same size. Earlier models may have a smaller petcook.