Coil failure

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Piero. Running 6 volt coil(s) in singular or parallel on 12 volts instead in series could do it. Another failure mode: Coils like to have a load on them, such as a spark plug. An unloaded secondary winding will arc at the point of least resistance which could occur inside the coil itself; once that happens and an internal arc path is established, the coil is likely toast.

Have you checked the rest of the ignition circuit and/or tested the coil(s)? The fault may be elsewhere in the circuit.

~998cc
 
998cc said:
Piero. Running 6 volt coil(s) in singular or parallel on 12 volts instead in series could do it. Another failure mode: Coils like to have a load on them, such as a spark plug. An unloaded secondary winding will arc at the point of least resistance which could occur inside the coil itself; once that happens and an internal arc path is established, the coil is likely toast.

Have you checked the rest of the ignition circuit and/or tested the coil(s)? The fault may be elsewhere in the circuit.

~998cc
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Hi.
Coils was two 6 V Lucas MA6 in series with Pazin sure fire I. E..
The rest of the circuit is those original with rectifier, diod and capacitor.
Stator charges well and the key switch is well firm.
Fuse never fault.
Thanks.
Piero
 
I had a coil from M.A.P fail. I took it apart and one of the wires fell off the + or - terminal. Lots of things can go wrong inside.
 
Piero
If you have access to a multi-meter, it's worth checking the coil resistances. See post by Mr Rick at the top of the following link:
https://www.accessnorton.com/NortonCommando/1974-850-commando-trouble-solved.25864/page-3
"Assuming the system you have is replicating the Lucas coils, you might wanna test even the new coil. Primary resistance (between the the + and - terminals) shd be near 1.7 -2 ohms.
Secondary resistance (between either post and plug wire terminal) around 5100."

Coils have been known to be incorrectly manufactured.
I have had problems with new Lucas coils and switched to PVL some time ago.
Interestingly when I measured the resistances of the PVL coils they were near identical to an original 1972 M6 Lucas coil that worked. The new Lucas coils did not match the old one.
Hope this helps.
Andy
 
the Lucas MA6 coils are produced by Lucas TVS in india quality is often erratic

i would swap them for the 17M6 lucas coils supplied in the green Lucas box
 
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