Magneto identification

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Magneto identification

Postby asterysk_usa » Thu Nov 07, 2019 2:32 pm

Could someone kindly identify the model of this magneto. The stamping is very difficult to read but some of the letters are visible


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1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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Re: Magneto identification

Postby Groily » Thu Nov 07, 2019 2:36 pm

Yup , it is an SR1.

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Re: Magneto identification

Postby asterysk_usa » Thu Nov 07, 2019 2:37 pm

Thankyou.

Does the L2 mean anything


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1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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Re: Magneto identification

Postby alanengineer » Thu Nov 07, 2019 4:26 pm

just be aware that those magnetos can be clockwise or anticlockwise in operation and yours does not have the green label that gives the first clue(arrow up or down) It has also been tampered with, with the bolt in the side, that indicated to me it came off something agricultural

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Re: Magneto identification

Postby asterysk_usa » Fri Nov 08, 2019 7:43 am

alanengineer wrote:just be aware that those magnetos can be clockwise or anticlockwise in operation and yours does not have the green label that gives the first clue(arrow up or down) It has also been tampered with, with the bolt in the side, that indicated to me it came off something agricultural


How can I check operation direction , I'm okay with dismantling a bit, just need to know what to look for, also could you perhaps share an image of the green arrow (I had a look online and couldn't find anything like that ).
1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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Re: Magneto identification

Postby Groily » Fri Nov 08, 2019 11:27 am

Having the mag on the bench makes it easy to check the rotation.

Anti-clockwise from the drive end is what you want on the bike.
Before doing anything else, you can stick a plug on the HT lead and holding the plug against the body to earth it, turn the mag smartly anticlokwise, and see if you get a spark. A good one will easily make a 1/4 inch spark with a smart flick, probably with the drive sprocket on to give you some leverage. But it could be that the points are filthy, the condenser is dead or something, so you need to look further . . .

If you take the plastic cover off, and then rotate the mag anti-clockwise by hand, you should see the points start to open just after - a few degrees only - a 'flip point' of the mag. (There are 2 per rotation.) The cam is set on a taper only, no key. So can be extracted and moved to the correct position if need be. The Lucas instructions here explain all and more you could want to know:
http://www.brightsparkmagnetos.com/libr ... %20SR4.pdf
For cam timing see Fig 9 on page 8.

Chances are, if the thing came off a motorcycle, it is set for anti-clockwise, as it's far more common than clockwise.

The nut on the side is not a Lucas bit as alanengineer says, nor I think is the insulator below it, which is askew. But as long as the screw and nut are insulated from earth, no problem.
That's where you could run a stop button from, which I mentioned in another post. It's also the place where a bendy tag is fitted on many mags, which you push till it touches the body, thus earthing out the low tension live side of the instrument. Far better on a bike, I think, to have a remote stop button, using a horn push or similar, on the 'bars. Then you can stop it quick if you have to, without having to operate the decompressor assuming there is one.

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Re: Magneto identification

Postby clive » Fri Nov 08, 2019 2:52 pm

If you fitted a tag on this mag it would foul the cylinder or be impossible to get your fingers at even on a cylinder with the correct cut away. The mag is from a stationary engine but is perfectly serviceable.
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Re: Magneto identification

Postby asterysk_usa » Sun Nov 10, 2019 6:41 am

alanengineer wrote:just be aware that those magnetos can be clockwise or anticlockwise in operation and yours does not have the green label that gives the first clue(arrow up or down) It has also been tampered with, with the bolt in the side, that indicated to me it came off something agricultural


Found the arrow !

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1954 AJS 18S Cyprus export (frame decode says 1954 but many components match a 1955).

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