Harley davidson coils

So the used replacement coils I put on last year have crapped out and I need new coils. I'm looking for a cheap new replacement and I have heard the HD 3 ohm dual fire coils will work as a replacement. Has anyone used them? Will they fit in the stock location with a 750 tank? My bike is a 80 650.
Thanks for the help!
Lee

 

I used the ones for the Honda CB 750... won't fit in the same location as mine (1985 xj700) but tuck them underneath the tank...3 years now and work perfect.

 

the 3 ohm part is right but there's not a lot of room in there.
how did you find a cheap Harley part?

 

They were $35 on eBay. I went with Rod1's idea and bought a pair of honda cb900 Coils. They are 2.5 ohm primary and 13 k ohm secondary and look like they will fit. I ordered them from rectifierregulator.com for $75 for the pair including new plug wires and new plug caps from ngk.com for $7.50. I will update after installation to let everyone know how it goes. I have to check my pickup coil tonight to make sure that is ok.
Thanks,
Lee

 

Lee...you have to install them underneath the tank, in the xj 700 won't fit in the original place...so I placed them underneath the tank.

 

OK I have finally received the coils (CB900) and mounted them. I mounted them backwards from the original with the secondary leads facing backwards and added a washer as a spacer on each side to get the primary leads away from the front of the frame. They fit under the tank and also under the 750 tank I installed. I have a good spark at all 4 plugs and the bike is starting. now for the problem... It will not rev at all and I am getting some backfire through the carbs and also from the exhaust. It is idling at 1000 rpm but will not go any higher. I have replaced the spark plugs, plug caps, plug wires and ignition coils (with CB900 coils). It has a spark at all cylinders, coils have 2.7 ohm resistance on the primary and 1-4 has 30k at the plug caps, 2-3 has 40k at the plug caps. The pickup coil has 700 ohm on each pair of wires. I haven't seen anything about backfires through the carb so I am making the assumption the TCI is bad. Has anyone had a similar experience with the engine running but not reving? are there any other items I may be overlooking that affect the timing? The carbs seem to be OK and it was running fine before the coils stopped firing that started this repair. I will post pics of the mounted coils in a couple of days when I can upload them.
Thanks,
Lee

 

I assume you are using standard copper core wire not carbon core for autos. That didn't work for my cb750k3 with Dyna coils and haven't seen it work on anything I have owned lately.

 

Yes I am using the copper core wires that came with the CB900 coils. The backfiring through the carb is what leads me to think it is the TCI now that I have spark.

 

your backfiring thru the carbs.....is most likely improper valve clearances and carbs that need cleaning....

 

I thought of that and that may be my next step. The thing is it was running great and I had finished a 200 Mike trip to the river. The next morning it wouldn't start at first then after about 10 minutes it started and I rode 200 miles home with no problems at all. Then the next day it wouldn't start at all and I wasn't getting spark to any of the cylinders. When I checked the coils one was reading 100k ohms on the secondary and the other was reading 0 ohms on the primary. It would seem that valves out of adjustment would cause a slow degeneration of ridability and the carbs as well.