Ignition coil
Ignition coil
Thinking of rewinding my ignition coil. Does anyone have any tips? I have not rewound anything since I was a kid..slot car armature!!
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boris tarpit
- Posts: 80
- Joined: 18 Jul 2007 20:50
- Location: caught between the twisted stars
Re: Ignition coil
. . I managed to rewind the source coil on my 3 1/2 it wasn't difficult just tedious - 3500 turns as I remember . . the wire is quite fine and I broke it once or twice which meant I had to start again . . . it is also much easier if the coil is removed from the backing plate and wires . . . I replaces the rivets with fine bolts with the nuts lock-tited on . . . happy winding . . 
No man is an island - except for the Isle of Man.
Re: Ignition coil
Yes it is a tedious job. What diameter wire dis you use..125?
I intend to completely remove the coil as you indicate.it is not possible to do it in situ on mine due to how the soldered tags are crowded.
I intend to completely remove the coil as you indicate.it is not possible to do it in situ on mine due to how the soldered tags are crowded.
Re: Ignition coil
Forget the 300 ohm figure!
I've never seen an original ignition coil that could ever have given a resistance that high. The wire used was just too thick to get enough turns on the bobbin to achieve it. I've measured several well performing coils at 220 ohm, but the actual figure is not very important.
It may be that the very first coils were wound with thinner wire and they changed to a thicker wire because of reliability problems, but the 'magical' and 'mystical' 300 ohm value still made it into the manual.
Modern wire has better insulation so you could the thinner 0.125mm wire, but I prefer the thicker 0.150mm. It's easier to wind and takes less time because there are fewer turns. I don't bother counting, just fill the bobbin making sure I don't make the coil too big so it doesn't fit.
The German Morinisti leave out the copper 'choke' plate that limits the coil voltage and use Transorb voltage limiters instead (like a bi-directional Zenner diode). This protects the coil from high voltage spikes that could degrade the insulation over time.
I've never seen an original ignition coil that could ever have given a resistance that high. The wire used was just too thick to get enough turns on the bobbin to achieve it. I've measured several well performing coils at 220 ohm, but the actual figure is not very important.
It may be that the very first coils were wound with thinner wire and they changed to a thicker wire because of reliability problems, but the 'magical' and 'mystical' 300 ohm value still made it into the manual.
Modern wire has better insulation so you could the thinner 0.125mm wire, but I prefer the thicker 0.150mm. It's easier to wind and takes less time because there are fewer turns. I don't bother counting, just fill the bobbin making sure I don't make the coil too big so it doesn't fit.
The German Morinisti leave out the copper 'choke' plate that limits the coil voltage and use Transorb voltage limiters instead (like a bi-directional Zenner diode). This protects the coil from high voltage spikes that could degrade the insulation over time.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
Re: Ignition coil
I share similar views as my last morini...30 odd years ago, had low readings but started fine.
The current bike has a weak spark but only gives a 130/140 ohm reading. It will not start hence my plan to rewind and see what happens.
Have you seen a working coil with resadings this low that still worked?
The current bike has a weak spark but only gives a 130/140 ohm reading. It will not start hence my plan to rewind and see what happens.
Have you seen a working coil with resadings this low that still worked?