Sam Cormier mentioned to me that he had a bad experience with a pattern spring from eBay India and I realised when looking in my lists that I know next-to-nothing about these retainers, least of all that there are three different concurrently listed parts numbers for the M01 alone - ignoring the earlier types and the twin-cylinder mags.

I "assume" the three variations relate to the location of the pillar. Bottom left or right depending on location of A/R cable and top left on some models ? I have examples of a couple of different length springs, but of course they aren't marked with part number or application and the Lucas lists don't show all types.

All Norton literature that I've looked at indicate part no. 463907 for the clockwise tight-wire AG4 magneto (spring pillar bottom left).

Lucas do indeed show this number in their lists into the late 1940s at least, along with two others - 463898 and 463899.



Current parts suppliers, if they show a number, generally refer to 463898 as "universal".

One trader shows 463899 as suitable for "right hand control spring"

https://bmhstore.bmh.com.au/electrical-magneto-ignition-c-38_11/magdyno-cover-clip-lucas-rh-p-628.html

and 463898 for "left hand control spring".

https://bmhstore.bmh.com.au/electrical-magneto-ignition-c-38_11/magdyno-cover-clip-lucas-lh-p-627

No trace there of the Norton 463907 which was a lower fixing with left hand control spring. In fact, this part number only occurs in searchable scans of period documentation.

As far as I can tell, the various makes were positioned as follows :-

Norton - left hand A/R - Spring Clip bottom left. (short)

Enfield - Left hand A/R - Spring Clip top right (long)

BSA - right hand A/R - Spring Clip Top left (long)

Ariel - right hand A/R - Spring clip bottom left (mid length)

Triumph - right hand A/R - Spring clip bottom left (mid length)

The clip obviously can't be mounted at the top on the same side as the A/R, but it can be at any of the other three locations.

Measuring roughly, the distance from centre pillar to centre cover seems as if it could be 1.6", 1.9" or 2.1"

So which two lengths are currently available ? Are the pattern BSA clips long enough ? Are they a bit too long on Ariel or Triumph ? The short ones seem correct for Norton...but the Norton part number is no longer mentioned.

E.&O.E. I've probably made some obvious simple mistakes trying to formulate my thoughts here.

Well, I don’t know if I’m the only one with issues with these things, but it’s the second original I break. Having trouble finding another I opted for an Indian knock off. Big mistake, although the pillar is quite rugged and well made, the spring is some sort of hardened steel which breaks at the slightest pressure. Junk, lesson learned. I had originally thought these things were somewhat standard, but oh no, that would be too easy. All kinds of sizes, lengths etc… Great bit of research!