Ignition Coil

GoldenMotor.com

Hicksy

New Member
Jul 1, 2008
26
0
0
Perth, Western Australia
I think my coil has died, no spark but the magneto runs the lights ok when pushed.

Has anyone used a 6 volt car ignition coil on their MB, seems like a fair enough swap...
 

matt167

New Member
May 20, 2009
420
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0
usa
seems like it may or may not work.. the stock coil ( actully called a CDI, but is just an epoxy filled coil on these ) is 323 ohms.. I misplaced my DVOM and can't find it.. I do have an original Delco Remy 6v coil off of my '51 Chevy that was still good, but I replaced it with a new 1.. If I find my DVOM I'll check the resistance to see if it's within spec
 

Junster

New Member
Jun 2, 2009
445
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Washington St.
Hicksy try disconnecting the lights. You maybe drawing enough current to kill winding that supply's the blue wire. Your cdi may have gotten a lil weaker from running on less power. If you do need to replace it Thatsdax has them for 8 bucks.
 

matt167

New Member
May 20, 2009
420
0
0
usa
Guys, the CDI is not a coil. Its a little more complicated than that. It is a capacitive discharge module. Here's some information that you might find interesting. http://motorbicycling.com/search.php?searchid=203574
Tom
in basic principal of induction, a coil would work, because the current pulse to energize the secondary windings thru induction are all it would need.. but to keep the mag alive, the ohms would at least need to be close..

it is not a true CDI ither, it's extremely close, but it uses the mag for the crank signal and closer related to an ignition coil.. a true CDI uses a crank trigger, which provides only the signal.. it would still need power from the the mag to energize the secondary windings, and some electronics to switch it ( ignition module ) so it gets induction to the secondary windings.. that is why most CDI's have 4 wires..


this of course is all theory because I'v never cut 1 of these coils open, but based on my knowladge of basic ignition systems
 
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MB-Monkey

New Member
Nov 19, 2008
462
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51
Manchester TN USA
the lights will kill the motor you may need to shortin the gap on your plug to around .020 also make sure the lights are off when starting then switch them on. it is a fine balance to get the lights to run off the white wire.
 

Hicksy

New Member
Jul 1, 2008
26
0
0
Perth, Western Australia
The lights are switched and off when I try and start it. When I put it in gear with the lights switched on and plug out I can see the power is getting to them. But still no spark. It's only done about 100 miles. I was thinking if the coil/CDI has died, it might be worthwhile getting something a bit more reliable.
 

Norman

LORD VADER Moderator
Jan 16, 2008
2,605
6
38
71
pampa texas
If your cdi is suspected of dieing get the right replacement cdi a lot of people have tried to use something different as far as I know none have worked. If your running lights you will need to run a closer gap 0.017 to 0.020 and if your spark plug is close to fowling or shorting out the light system will find it, the lights will still come on when pedaling it but the ignition will not fire if you can turn off the light completely and the plug will fire then the cdi is fine.
When the cdi fails its dead for the most part it usually don't work then stop and then work again. inside of the cdi is a coil and resistors, a very small circuit board with electronic components etc. I'm not sure just how it works as I have not found a trigger coil per say in the mad coil winding I've taken the mag coil apart and the cdi box it's a booger with it bedded in epoxy my soldering iron won't keep up with enough heat to crumble the epoxy to get it to fall off easily . I was wondering how it all works myself until the makers can show a diagram we will all be wondering unless someone trained in electronics can look at one a tell how it all works I guess we are going to not know for sure.
Norman