replacing coils with a harley davidson coil

I understand that the 2 lucas coils can be replaced with a single Harley Davidson coil. Can anyone who has done this share with me what kind of coil that is used and the installation procedure. Thanks Drummer99

It all depends on the ignition you have, if it's a Boyer or the like, any dual output coil with no less than 3 or 4 ohm resistance will do. Some ignition systems can tolerate lower resistance coils but not a Boyer.

Jean

I have successfully used a 3 ohm dyna dual coil on my commando since 2001. I used it first with the original black box boyer and then with the red box microdigital boyer. I've never had an issue with it since it was installed.

My coil, which was bought in the year 2000, looks like this. The new one's may look different or be a different color...



As Jean said, you have to consult the specs on your electronic ignition to know what resistance it requires from the coil.... I know the 3 ohm dyna works for the 2 boyers I have, but I don't know whether it works for lucas rita or pazon...

The Boyer, the Tri-Spark, the Pazon and the Wassel will work with 3 to 5 ohms of primary resistance, but seems to favor 3 ohms as the best number. The Harley coil you reference is a 5 ohm coil that will work with the EI's referenced above, but is better suited for points ignition.

o0norton0o said:

I have successfully used a 3 ohm dyna dual coil on my commando since 2001. I used it first with the original black box boyer and then with the red box microdigital boyer. I've never had an issue with it since it was installed.

My coil, which was bought in the year 2000, looks like this. The new one's may look different or be a different color...

As Jean said, you have to consult the specs on your electronic ignition to know what resistance it requires from the coil.... I know the 3 ohm dyna works for the 2 boyers I have, but I don't know whether it works for lucas rita or pazon...

Click to expand...

I use a double ended coil off an early Honda with my black box Boyer. I've thought about buying a microdigital Boyer - are they good ? Is that the programmable model ?

acotrel said:

I use a double ended coil off an early Honda with my black box Boyer. I've thought about buying a microdigital Boyer - are they good ? Is that the programmable model ?

Click to expand...

I don't think the red box micro digital is programable. Maybe someone else knows more about them than I do. I have used both boyers. They both worked fine. I changed to the micro digital so long ago that I can't remember what the differences are... Sorry, I know there's a difference, but I can't remember what it is. Maybe go to the website and read up on it a little bit.

Drummer99 said:

I understand that the 2 lucas coils can be replaced with a single Harley Davidson coil.

Click to expand...

Why would you ? I have original lucas 12v coils (73) and Trispark for 8 years. Fat blue spark and plugs are clean. Idle is strong and starting is super easy.

I would not swap.

Cheers

Have run a similar Rev-Tech Harley-type coil (4.5 Ohm primary) for quite a while also. I tend to keep my bike stock looking but I think it looks a lot cleaner under the tank with the Harley coil. I took off the Lucas coils right after Gordon Jennings' great coil test in Cycle magazine in the '70s. (I went to a pair of large Ford car coils back then.)

I have a 5 ohm Dynatech on mine, went for the lower amp draw as my 120w alternator struggles under 4000 rpm when lights are also on.

The Harley coil you reference is a 5 ohm coil that will work with the EI's referenced above, but is better suited for points ignition.

Click to expand...

Any reason why? Spark from the weaker 5 ohm jobbie seems better than my old PVL coils. I even fitted cheap old copper core Champions and they are working well with non resistor caps and copper HT lead.

Keith1069 said:

I have a 5 ohm Dynatech on mine, went for the lower amp draw as my 120w alternator struggles under 4000 rpm when lights are also on.

The Harley coil you reference is a 5 ohm coil that will work with the EI's referenced above, but is better suited for points ignition.

Click to expand...

Any reason why? Spark from the weaker 5 ohm jobbie seems better than my old PVL coils. I even fitted cheap old copper core Champions and they are working well with non resistor caps and copper HT lead.

Click to expand...

Points like higher resistance for less current flow through them; remember the ballast resistor? The lower the resistance, for points, the shorter their useful life span. Some of the very early electronic ignitions turned the points into a simple switch. You can still purchase the Dyna system for BMW airheads that do the high power switching in the electronics and use the points/AAU as very low power triggering, thus extending the life of the points and limiting their wear to the points heal(s)

Electronic ignitions begin to lose spark above 5 ohms and run poorly at 6 ohms and erratically above that. Below 3 ohms and the internal current flow approaches or exceeds 5 amps which the units do not tolerate for long.

The Boyer MicrDigital is not programmable; its claim to fame is that it is very (low) voltage tolerant; important on motorcycles with electric starters that can draw down system voltage, and the Boyer MD has a patch of firmware that stabilize the idle speed, as do most modern others EIs. Programmable EIs are stupid expensive, and by the time they are installed and dyno tuned you will have spent well over $1000, certainly not a "street" smart option, but may give the highly competitive racer an edge, don't know. I have no experience with crank triggered electronic ignitions, but I would wager that they are more consistent than ignitions triggered off the ends of jumpy cams?

Let me ask a general question. How many members of this forum that have installed EIs have actually verified the accuracy of their timing scales? I have observed over many rebuilds that the timing scales very as much a 5 degrees, nice that the Mk3 are adjustable.

Guys thanks for all the input should I go with a dual fire or single fire coil ? I know the Dynatec coil referenced is dual fire is there any issue with the 2 plugs firing at the same time? Thx Drummer99

Good point about verifying the timing scale accuracy RoadScholar, I just did mine & found it to be off by 2', as in (true 28' BTDC will read as 30' on the scale). For what it's worth I just installed a single, duel output coil & TriSpark from CNW. Nice, clean & simple to install & use. I've used Dynacoils on Guzzi's in the past & they were a great improvement over the stock sh#}*t coils but never had one on a Norton. I'm sure if you stay within the 3/5 ohms they are great. I liked the clean way the CNW coil such I think is a Accelerate has the wire posts on the front. It's just a nice clean part & although I've only had time to do about 10 miles, so far it's working great.

I have been using the HD dual fire coils with all makes of electronic ignitions with great success for years. Ohms should be around 3 . All of my bikes have them......Skip

phillyskip said:

I have been using the HD dual fire coils with all makes of electronic ignitions with great success for years. Ohms should be around 3 . All of my bikes have them......Skip

Click to expand...

As I mentioned earlier, electronic ignitions like 3-5 ohms, virtually all Harley coils are 5 ohms, if yours are 3 ohms, no skin off anyone's teeth, go nuts!

B.

I tried the Hardly Ableson Screaming Beagle dual output coil with my old style Boyer and the 9 month old HD part shit the bed when I was 1500 miles from home. A hitch back into Tahoe, CA and taping a couple NAPA 6V coils to the down tubes got me home. My conclusion was that HD parts are only suitable for motorcycles taken for a ride on a trailer...

6V Lucas or Bosch have never let me down.

Greg

gjr said:

I tried the Hardly Ableson Screaming Beagle dual output coil with my old style Boyer and the 9 month old HD part shit the bed when I was 1500 miles from home. A hitch back into Tahoe, CA and taping a couple NAPA 6V coils to the down tubes got me home. My conclusion was that HD parts are only suitable for motorcycles taken for a ride on a trailer...

6V Lucas or Bosch have never let me down.

Greg

Click to expand...

Harley didn't make the coil; in all likelihood it was built by Dyna. RPC has been selling Dyna coils for over 10 years, we had one fail about 4 years ago, they are warranted through the manufacturer and was promptly replaced; I offered to overnight a replacement, but Dyna beat me to it. I realize that such excellent customer service doesn't take the sting out of being stranded, you have my sympathies. The Norton gods have insured that I got my exercise, walking and pushing (plenty) back in the day for any number of failures, some induced be me, some induced by "well intended" design/manufacture; these character building experiences taught me the value of taking a detailed "systems" approach to building/repairing our beloved marque...

I tried the a Knology one from a Harley place. It had the correct resistance for the boyer. It got too hot I think and started to leak oil. I still have it in my Norton junk box. Stay with stock coils for me.