Lucas N1 Magneto Siezed

Information relating to the Matchless G3 or AJS Model 16 350cc Heavyweight
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Diana3899
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Lucas N1 Magneto Siezed

Post by Diana3899 »

I am hoping to get my M16 ready for the Jampot but things are conspiring against me. A few days ago I lost the spark and on investigation I found that the armature is locked solid and will not rotate in any direction. I took the mag off the bike today and even on the bench it will not rotate. It was delivering a nice spark until a few days ago. So, does anyone have any Idea what has caused the armature to lock up.
Groily
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Re: Lucas N1 Magneto Siezed

Post by Groily »

Am guessing it stopped sparking when it was hot - but now is seized solid?

Unless it is a mechanical failure, with broken metal parts or a contact breaker that has gone askew jamming it up, it will be because the insulation of the coil has melted and then set like glue when it cooled down.
The coil will probably be an original Lucas one, with shellac used for insulation - modern rewinds don't use the same materials, so shouldn't seize in this way.
If it is this (and it's not uncommon sadly), then the old coil has actually done pretty well to be fair to it - but a full rebuild will now be needed I'm afraid.
To know for sure, you could detach the contact breaker (then see if the armature turns), and if it's still solid take off the end housing it sits in, and see whether the armature is glued solid by dirty brown goo.

It is quite hard to believe the strength of the 'set' when this calamity befalls. But seeing is believing unfortunately . . . .
SPRIDDLER
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Re: Lucas N1 Magneto Siezed

Post by SPRIDDLER »

Groily wrote: Mon Aug 08, 2022 9:28 pm Am guessing it stopped sparking when it was hot - but now is seized solid?

Unless it is a mechanical failure, with broken metal parts or a contact breaker that has gone askew jamming it up, it will be because the insulation of the coil has melted and then set like glue when it cooled down.
A chum had that happen after a longish test run with a newly fitted stator and rotor. He put the bike in the shed and next morning the 'engine' was locked solid. The rotor had been making the merest contact with the stator, heating it up. He was unaware that the stator potting material had softened and migrated from the stator but by next morning it had hardened locking the stator and rotor together.
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Pharisee
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Re: Lucas N1 Magneto Siezed

Post by Pharisee »

I had something similar happen to the alternator of my '71 Triumph. It didn't seize up the engine but it did make a mess and necessitate a replacement.
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spookefoote1956
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Re: Lucas N1 Magneto Siezed

Post by spookefoote1956 »

I've got a Thorspark unit advertised for that mag in the For Sale section.
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Diana3899
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Re: Lucas N1 Magneto Siezed

Post by Diana3899 »

Thanks for response chaps, it happened after a long hard test ride on a hot day it sounds like the shellac may have melted and glued up the works as suggested. I will have to have it rebuilt so will take it to the Kempton Park mag man next month. In the meantime I will fit an old N1 I have in the shed and hope that will get the bike going again.
g80csp11
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Re: Lucas N1 Magneto Siezed

Post by g80csp11 »

alternative route is exchange unit from spares scheme , comes with all the guarantees that you get from APL and they are in stock , you could still get it and make it to the Jampot
Diana3899
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Re: Lucas N1 Magneto Siezed

Post by Diana3899 »

Feedback time: today I fitted a spare N1 Mag I had in the shed and not too sure how good and reliable it is. I have just ridden around the block a few times and she started ok from cold and also from hot when I got back to my garage. Tomorrow, I will take her out for a good run and if all is ok I will take her to the Jampot rally in Wales next week. If not, I will have to take a BSA or Triumph as I don't want to miss the event. Thanks again for your replies and suggestions.
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spookefoote1956
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Re: Lucas N1 Magneto Siezed

Post by spookefoote1956 »

Hope it goes ok Di
Hail Joe Lucas ............ Prince of Darkness!
All my bikes are original........ to me!
"Creativity is your intelligence having fun" Albert Einstein
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