1938 square foue Magneto sprocket

[ralph thetford]

I have just set the points on the Magneto but on nipping up the nut on the sprocket it moves the Magneto shaft slightly and of course moves the points out of setting---I have had about five goes at this and every time the shaft move slightly-----Does anyone have a safe and sure way of holding the Magneto shaft while nipping up the end sprocket nut.

Regards Ralph Thetford

[JohnnyBeckett]

i line up timeing with chain and sprocket on put the nut on by hand and get a socket or a tube to tap the sprocket on or just nip it up a bit with a impact gun then you can tighten it up

[paul.jameson]

You need two things. First, the sprocket taper should easily bind on the shaft taper. If it doesn't, apply fine grinding paste and grind in to improve the fit but make sure you remove all traces afterwards. Second, the nut must run down the thread on the shaft freely. If it binds, it will move the shaft. Again, any binding here can be rectified with fine grinding paste. Once you get these two things right, the only remaining problem is backlash in the drive train. Trial and error will remove this.

Otherwise, use Johnny's advice and tap the sprocket onto the shaft then tighten the nut.