12v ignition coil recomendations?

[kmev]

Need a recommendation for a good 12v ingition coil that would be a good match with points and an Electrex World 120 watt, 12v generator system. It doesn't need to be stock-looking, just needs to fit under the tank.

My local speed shop is not helpfull with customers who don't have a specific year and model of bike, so I won't have any luck simply asking for a random 12v coil.

Also, are there different condensors for 6 and 12 volt? How about a spark plug - are there different plug numbers for 6 and 12 volt?

Keith

[wcorey]

Bosch 'blue' coils have long been popular, reasonably priced and have withstood the test of time. Not sure about fit for your application, they're a typical size automotive form factor.
I really like the 5 ohm Dyna coils but only if I find them cheap used. I've also had good luck with various old Honda coils with the integrated plug wires.

Bill

[MotoMike]

both 12 and 6 volt coils step up the voltage to several thousand volts so that a spark will jump across the plug electrodes when the points open. So there is no need to change your points, condenser or plugs. I don't know what your intended final use is, but I'd probably ask to look at the coils at your parts store and find one which is a 12volt coil that will fit well where you want to use it. Those Bosch blue coils were popular replacement coils for the Moto Guzzi Eldo's and it seems I recall some of the VW coils are smaller and would work well in the stock location. 5 ohms is probably a good figure. the lower the ohmic value, the more demand it will make on your system.

[DewCatTea-Bob]

By: kmev...
" Need a recommendation for a good 12v ingition coil that would be a good match with points
It doesn't need to be stock-looking, just needs to fit under the tank. "

____ You ought to be able to fit a '12v' ign.coil made for old Mercury outboard boat-motors (made by Bosch), which used to be the best ign.coil ya could get which would still fit within the stock coil-bracket.
__ I assume that you believe you need a 12-volt ign.coil because your system has been converted-over to 12-volts. ...
But a standard "12 volt" ign.coil is not necessarily much different than any common 6v.type, as it's merely just a 'rating' concerning it's primary-windings ability to handle expected current & resultant heat.
__ I believe that if Ducati could've more cheaply acquired bigger/better (more modern like) ign.coils, then certainly they would've recommended larger s.plug-gaps (for easier starting, etc.).
I suggest that rather than installing some "12 volt" ign.coil, instead try the stock (6v.rated) ign.coil along with a 'ballast-resistor' ...
That way you can get about twice the sparking-power and can then increase your s.plug's gap out-to 35 to 40 thousandths and reap the benefits of such.
The purpose of the added ballast-resistor is to protect the ign.coil from getting overheated,, as after the resistor heats-up (as intended), it then subdues current-flow down-towards a more normal/stock-like level (which keeps the coil from becoming too hot).
The substantial & intended benefit of this (series)- arrangement, is to allow a cold engine to enjoy a hotter ign.spark, (which helps to get the engine started), due to the fact that a cold ballast-resistor allows more energy to pass into the ign.coil,
(yet prevents that from continuing for too long, [by warming-up & taking the heat which the coil would otherwise have to endure] ).
Such ign.ballast-resistors come with varying resistance-values (between .5 to 3 ohms), and in combo with a 6v.coil, a b.resistor with a near matching (heated-up)- value, ought to be chosen.
__ When I first converted-over to a 12v.system, I of-course also wanted the resulted hotter-spark as well, so I simply left the stock-ign.coil just as it originally was,, and it ran okay like that (for all the time I had left it that way) but, I did check the ign.coil for any increased heat and found that it could get too hot to (comfortably) keep my hand tightly-grasped onto, (which is why I didn't trust to leave it that way for long).
____ Here's a link to a b.resistor I found currently on eBay, although probably not your best-choice, (as I only included this so that such a resistor can be easily found).
http://compare.ebay.com/like/1305572092 ... s&var=sbar
That unit I gather has a cold-value of .75-ohms and a fully warmed-up value of 1.5-ohms. _ I'd prefer one with an even lower cold-value, and with a warmed-up value that's NEARly equal to (but certainly not greater than) the resistance of the ign.coil.


Dukaddy-DUKEs,
-Bob

[kmev]

I picked up a ballast resistor - going to give it a try. It won't fit under the tank next to the coil, so I'll probably mount it under the seat near the regulator.