Lucas MN1E Magdyno on my 1938 square four

[ralph thetford]

I was setting up the points on the MN1E magneto on my 1938 square four when I realised that instead of the fibre heel touching the cam ring to open the points, the points were being opened by the head of the screw holding the leaf spring to the fibre heel----(ie the screw has around head and is catching the cam ring and opening the points.)------Has anyone had a similar problem ?----Should the screw have a countersink head ?

Regards Ralph Thetford

[pete.collings]

I am not familiar with the setup with a MN1E magneto, but recently on a K2F magneto I had obtained I found a screw retaining the leaf spring was not screwed fully home, and was making contact with the cam ring, and interrupting the points circuit. Shortening the screw and making sure it was fully home resulted in a nice spark from a previously unresponsive magneto!
The correct leaf spring retaining screws have a flat head with very little raised area, and can be difficult to screw home. You should ensure there is no contact with the camring at any point of rotation.
I think the screws are 6BA thread, so someone who has lost a screw (they are prone to fly anywhere due to the spring slipping on tightening as it is hard to get the threaded portion at the correct angle to the points block) might have used a 6BA screw with a raised head.

[john.whiting]

yes, had a look at a couple ....screw is dome head and very close to the ring......I suspect fibre block wear is the problem, block needs renewing,or maybe it can be packed up with a plastic shim........on the subject of mags,can a points plate for a BTH be obtained......I have several that I want to reverse the rotation.........the BTHs are off stationary engines ,and always seem to be wrong rotation for a bike.........except a Norton......the story goes Norton reversed the rotation in 1934 to take advantage of a cheap job lot of mags meant for Listers....not changed again until 1948

[ralph thetford]

Thanks John, I have slighty filed down the screw and it now clears OK ---Regards Ralph