The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: bakerlonglegs on 09.06. 2019 09:31
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Hi, I'm struggling to wire up my magneto, the cut out in particular. Please can I ask for your advice?
The metal contact inside the end cap is very close to the top of the thread, so I can't turn the connector very far before it's jammed up against the contact. I hope the pictures explain that better than words! However, it is very likely that I'm doing something wrong, have forgotten a basic thing or some other muppetry on my part. Is this is a common thing and what should I be doing to fix it?
Many thanks in advance for wiser heads than mine!
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I think the problem (at least, it's the one I had) is that the pattern end-caps aren't made identically to the originals in that the centre contact is too high. My solution was to shorten the acorn. Doesn't give the thread any more purchase but it looks better.
I did think of Dremeling the centre contact down a bit and probably will next time she's in the workshop.
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Ditch the brass washer
This will allow the cap to screw down till the center electrode pinched the wires.
This is a kill switch, not a spark plug lead
A single strand of wire in contact with the electrode will do the trick.
Put a tight fitting O ring on the outside & inside of the cap
The inside one will pinch onto the wire much like an olive on a water pipe & the outside one stops a lot of water getting to where you do not want it to go.
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Thanks very much for the replies and advice guys!
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are we forgetting that the final contact is at the kill switch ( so the contact in the maggie has to jam up against the contact) or have I missed something
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Bill, you are right, but that seems not a problem.
I'm not debating with Trevor here, and my idea will probably not help enough. Nevertheless, it seems that the wire emerging from the washer is twisted and bent over, leaving a tall mound of wire. The strands of the wire should be splayed evenly around the disk of the washer, leaving the wire about one strand high. The contact will, uhhh, contact several strands of wire at the center.
Richard L.
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Looks to me its just the wrong bits. The Acorn Nut comes in different lengths, long, which you have, short, which you need. The actual lead only needs to be relatively thin, yours looks the size of a standards HT Lead, the disc is typical of a HT fitting.
Internet search for Lucas Acorn Nut will bring up a fair number of images, including one with a waterproofing boot.
For now, drill out a little bit of the centre of your existing nut so that the nut clears the centre contact and can be screwed further down into the cap. The lead just needs a homespun contact soldered to its end, which will fit in the new hole, typically the sort found in an inline fuse carrier. Screwing the nut down clamps it against the cap contact. A pop rivet crimped to the end of the lead would do as a short term fix. Crude but effective.
Swarfy.
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And be careful when sourcing fresh acorns to know whether what you're ordering is 1/2 BSF (correct, original standard) or 13mm (incorrect, commonly found on pattern parts). Often won't interchange - all slop, or too tight to do up, depending which way things are.
But Swarfy's fix would do it, in conjunction with getting rid of the fat lump of wire sticking out the end.
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Which rating should the cutout wire be please ?
Incidentally what rating are the other wires used in the harness and where is the best UK source please ?
Thank You in advance ,
Steve ..
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Next to SFA. It's only earthing out the mag after all.
For general wiring I use Vehicle Wiring Products who sell (or used to) cable by the metre.