D's double coil

[Gerry w 2]

I'm wondering if in the D's and 18Auto's with the K engines is there a reason they used the double coil instead of two singles? Is there a difference in output, input? I KNOW there's a difference in cost! Will something not work if they are switched for the other? Could I damage a part of the engine if I was to try the two singles?

Any info would be most welcome, electrical is my weakest link and although my 20Auto is running strong I would like to be prepared in case.

Thanks in advance,

Gerry

[73-18 automatic 8]

I have seen people use two coils but do not know that much as far as how

[Gerry w 2]

Thanks for the reply! I'm getting the idea I'm not the only one who doesn't know why!

Thanks though!

[TT-(Moderator) 1,162]

Many opposed twins use a dual-fire ignition system which is a fancy way of saying that both spark plugs fire at the same time via a two-tower coil and one set of breaker points. While the one cylinder is approaching TDC on the power stroke and firing, the opposite cylinder is on the exhaust stroke and firing the plug does absolutely nothing.

Although two separate coils could be installed, I would think that the increased "load" on the breaker points would cause premature failure of the contacts.

If you're seeking a cheaper alternative replacement coil, look no farther than Harley-Davidson.

Here's a LINK to a coil currently on eBay. You probably won't find one much cheaper, but the OEM number is on the listing if you'd like to shop around for yourself.