Lucas ksa1 magneto

Information relating to Matchless and AJS Models built prior to 1939
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Tazmantic
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Lucas ksa1 magneto

Post by Tazmantic »

Hi anyone have a pic or exploded diagram of the manual Advance and retard mechanism as it’s missing on the mag I bought.

Cheers
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Groily
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Re: Lucas ksa1 magneto

Post by Groily »

This is hard to describe, but the parts are like on the magneto section of the MDB magdynamo, and several other pre-war Lucas ringcam instruments. They are not the same as the parts found on later magnetos.
The outer cable's lower ferrule is retained in a threaded adjuster which screws into an eccentric 'lid' which screws on with a single offset screw to the threaded hole on the cb end, 2BA. They are handed.
The cable passes right through a cylindrical brass 'plunger' which is milled to a curve on one side for most of its length to clear the camring, but with one section left as a 3/4 circle lug somewhat 'off' the mid-point. It is effectively 'fenestrated' because the hole up the middle is broken into when removing brass to create the curved shape. This lug locates in the slot you'll see in the camring and can push / pull it to advance and retard the ring. They are also handed.
The cable has a soldered nipple on the bottom, which is located by the aid of a split washer that goes round the inner cable snugly and locates against the bottom of the brass plunger. There's a plug screw that blocks off the hole at the bottom of the big hole bored in the monkey-metal casting.
The plunger is bored to take a spring that goes pretty much full depth within it and holds it in position (against the friction of the handlebar lever) anywhere between full advance and full retard.

I can't find an exploded view of the KSA although there must be one somewhere, but the pix in the link, page 11, show the elements except for the plunger - see parts numbered 216, 217 and 223. Also in the file (a bit further 'up') there are references to parts 213 and 220 without illustrations - these are the plunger part numbers.

I have a set of the parts, not sure which 'hand', which I use for test purposes on these sorts of magnetos. See pic (no spring unfortunately). I have also made the bits in the past, but it is a boring old job!

Here's the MDB link:
http://brightsparkmagnetos.com/library/ ... 0_1929.pdf
and here are the lid and plunger:
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Rob Harknett
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Re: Lucas ksa1 magneto

Post by Rob Harknett »

Look here for 1925 - 1934 AJS hand book & 1925 - 1927 parts list. www.archives.jampot.dk
Groily
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Re: Lucas ksa1 magneto

Post by Groily »

Thanks Rob.

Page 139 of the '25-'27 list shows the bits, on a page with period magdynamo parts. The booklet also shows a K series horseshoe magnet magneto elsewhere - all the same bits (bar the question, just possibly, of handedness).
H1427 = plunger, H1428 = spring, H1429 = eccentric lid and H1431 the 2BA screw. (They are upside down in the sketch.)

Couldn't find anyone that actually sells these bits when I looked last evening (although I bet there is a person somewhere) but with patience they can be made laboriously if they must be. Key thing is getting the lug in the right place to allow full movement of the camring.
Greybeard
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Re: Lucas ksa1 magneto

Post by Greybeard »

One point of interest relates to the soldered nipple in the lower end of the brass plunger. Ive just replaced the cable on the mag for my 1926 AJS and was suprised to find that the nipple is actually threaded and screws into the plunger. Ive never come across that before. So if the cable doesnt want to come out, try unscrewing it. I also found that the cable adjuster was threaded M6 :? Were they adopting metric threads at that time to align with the metric spark plug threads?

Steve
Tazmantic
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Re: Lucas ksa1 magneto

Post by Tazmantic »

Thanks guys looks like I have to keep a look out for some parts as it’s not as simple as I first hoped

Cheers
Everyday’s a learning curve.
Groily
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Re: Lucas ksa1 magneto

Post by Groily »

Greybeard wrote: Fri Apr 08, 2022 8:59 pm was suprised to find that the nipple is actually threaded and screws into the plunger. Ive never come across that before. So if the cable doesnt want to come out, try unscrewing it. I also found that the cable adjuster was threaded M6 :? Were they adopting metric threads at that time to align with the metric spark plug threads?
Steve
I'm surprised too! Never seen that, and it means a mod to the plunger by someone I think as they weren't made like that AFAIK- or none of the couple of dozen or so I've seen have been anyway.
Cable adjusters? Well, I guess people use what they can find when making up replacement cables. I know I do now and then! . . . So probably a thread tweak on the lid too.
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