Hitchcocks Forum

On a Lucas M01L, How many teeth should be on the dynamo drive gear pair. Also, what decides the rotation on each unit., and finally what makes the dynamo + or - earth. -Is it just the control box??

Can't help with the number of teeth but I suspect the ratio will be 2:1. Perhaps someone will have their magdyno on the bench and will be willing to count them! Magnetos are normally made clockwise or anticlockwise, and, as far as I know, can't be changed. The armature, magnets, points, and the pickup and earth brushes are positioned relative to each other to provide the biggest spark when the points open and if the magneto was run in the wrong direction this wouldn't happen.
The dynamo question is much easier. Lucas dynamos can be used either as positive or negative earth and can rotate in either direction. After the battery has been fitted, a lead is connected to the 'live' terminal - this will be the positive terminal on a negative earth system and the negative terminal on a positive earth system. The other end of this lead is touched briefly two or three times to the (unconnected) F (field) therminal on the dynamo. This 'polarises' the field coils to suit the earth system being used. A mechanical control box will work with either earth system. An electronic one, however, has different internal components for the two earth systems so can't be altered (they're usually switchable between 6 and 12 vols systems easily, though).

Cheers StuartL, What you are describing is "flashing the field"? So it looks like that is all that is necessary to change dynamo polarity?As for the magneto, I have been told that rotation can be converted , but I have no idea how this is done (Yet!)

Managed to find a modern solid state regulator that will fit inside the old mechanical 6v regulator case, so were cookin with gas now, - just need to get to grips with the magneto, then I can go back to the crank assembly. Anyone know how to align a crank to better than 3 thou" ?