Ignition Coil Rewind Advice

[SoloFrenos]

Hi, I need to rewind the ignition coil on my alternator, i understand from previous posts that i am best to go for 0.15mm wire and ignore the 300 ohms resistance mentioned in the blue book, but can anyone recommend where i can buy the wire from and an exact spec? I do not just want to by 0.15mmm copper wire off ebay as i want to make sure i have the right stuff. Also i need to replace the bobbin as the old one fell to pieces, i understand that one from various Vespas and lambrettas fit but none of the ones i have found on the internet list sizes so i cannot tell if they will, so again i just wondered if someone could advice me one which ones will fit and where i can buy an empty bobbin from?

Thanks, Tony

[3potjohn]

Have a look at wires.co.uk for a supplier. i expect someone who has actually done this will be along soon. I think there's some info on the Dutch Morini site. Mind you the way this weather is i might as well do mine, either that or go to Motorcycle Live and look at the Guzzi V9. And i thought it was a Volvo.
John

[EVguru]

I've come across a few factory 300 ohm coils, but by far the majority were 220 ohm. The later used a larger diameter wire and there is not enough room on the bobbin for enough turns to get to close to 300 ohm.

It's voltage that matters to the ignition and for a given alternator rpm, that's dependent on the magnetic field strength and the number of turns on the coil. The resistance is of little importance. It's worth noting when you wind a coil, so you can see if it's changed over time (lower resistance equals shorted out turns), but thinking you've got a problem because your coil 'only' got to 260 ohm is complete nonsense.

More turns does equal more 'spare' voltage, but you could in theory go too high and possibly damage the ignition boxes. The lambretta coils obviously use more turns of thinner wire as they measure at over 500 ohm. The high resistance might cause problems charging the capacitors in the ignition boxes. The Lambretta coil is designed to power one ignition box, not two.

I bought a couple of ebay item; 251457039671

They have the high resistance coil, but the former will fit (with a little cleaning up). They're cheap enough that you could strip off the existing coil.

The last coil I rewound, I used 0.132mm wire (because I had a reel) which allows for more turns than an original 0.15mm wound coil.

[EVguru]

I just peeled off the outer insulation on one of the Indian Lambretta coils. The wire measures 0.123" over the insulation, so I'd guess it's 0.1mm copper diameter.

[norbert]

My experience is that the problem with starting the engine begins with less than 170-180 ohms

[3potjohn]

My coil was 186 ohms when i got the bike.It bump started OK, and i live on a hill but needed a few brisk kicks to start it otherwise. Once rewound no problem at all.

[SoloFrenos]

Thanks John and Paul, Wire and bobbins ordered. Need to get myself set up for a comfy couple of hours ion the garage winding now )

[Ming]

Hello, I rewound a coil some years back (it's 'featured' on the NL site) - was a relatively easy thing to do.
Wire is not a problem, but I've been looking for spare coil formers ever since (empty ones) with no success so far.
As suggested, you could strip a scooter one.
I have most of the bobbin of wire left over, so if anyone wants some, let me know what length you want and it's yours for the postage.

[Tim]

Have ordered one of the lambretta coils from India and I have a coil of wire ready to do a rewind but I'm not sure from the above posts whether I really need to - i.e. is the voltage too high for the ignition units?
Also I understand that there is a voltage limiter of some description in the system which I thought was for the ignition coil but not sure given Paul suggesting risk of damage to ignition units. Also is there a better alternative to the voltage limiter - it looks a bit old tech?
Grateful for any light you can throw on this issue!
Tim

[EVguru]

Take a look at Soren's ignition videos, he goes into the voltage limiting.

https://www.youtube.com/user/Sir1HH

[Tim]

Yes I see he recommends ditching the old style voltage limiter in favour of two or three diodes in a heat sink sited probably near the fuse panel. Has anyone done this mod?
Tim

[benshannon]

Hi Guys,

This seems like it may be the cause of my starting issues. I am learning the bike and wishing to do as much to it myself as possible.

firstly, how do i check how many ohms it is giving out?

could i redo an ignition coil myself?

Id rather not go to NLM if possible. not for the money side of things, but if i dont ever do it myself i wont learn.

Thanks for any help recieved

[3potjohn]

Hi as far as memory serves,you need to remove the right hand side panel,then looking at the fuse box area,locate the green wire coming from the coil.pull the connector off the spade terminal and check the resistance across them. Can be in the range 180-250-300ohms.Lower is worse.The connectors,being old maybe somewhat fragile. i opted to pay to get mine rewound,but if I had say two then I'd have a go myself.
Well i think that's right.......
john