Dyna S coil voltage question

Hi, It has been a while since I last posted anything here but I do still visit when I can. My question concerns the voltage drop at the coils on a dyna s ignition. My bike, which is a 1977 kz1000 ltd, started to miss recently and in my troubleshooting I checked the voltage at the coils. I have the green dyna 3 ohm coils. I also did the coil relay mod when I restored the bike in 2005. When I measured from the positive battery terminal to either of the plus coil connections I read a .6vdc drop. This seemed ok to me but when I measured from the negative battery terminal to either of the minus coil connections I read a 1.2vdc drop. Looking at the wires coming off the dyna pickups it looks to be around 18 gauge and the harness is about 3 feet long. Just wondering if this looks normal and if it was worth making a new harness out of 16 gauge wire.

thanks,
Len

Just measure the voltage across the battery. Then measure the voltage across the coil primaries (2 input wires), and subtract tfrom the battery voltage to determine the difference.

With a coil mod on there, the voltage should be the same as battery. A little less I would say is OK, but not a .6V drop.

Make sure your grounds are excellent, expecially the one from the reg/rect unit.

Remove the headlight and fuel tank and seat, and start pulling apart, cleaning, and firmly re-attaching every connector on the bike, one at a time. You will be surprised at the number of green/powdery connections there will be, even after having cleaned them previously.

Make sure to spray them generously with an anti-oxidizing contact cleaner spray when cleaning.

Good luck.

The large drop from the coil minus to the battery negative is not unusual (in the 1 to 2v range) because the Dyna S module will have a drop on it due to the way transistors work.

What you want to measure is from the coil minus to the Dyna S. The Dyna S grounds to the engine, so make sure you have a good ground to the engine from the battery negative.

Another place of posible trouble will be the Dyna supplied "Splice". It's an insulation displacing connection that over time will get corrosion and become intermittent.

I'd recommend soldering the joint and then covering it with heatshrink tubing for a much better electrical connection.

Thanks for the replies. I forgot that there were active components in the dyna pickups. I will go over the connections and grounds to see if anything looks corroded or loose. By the way, I like your avatar MFolks. I worked ECM on F4 D's during my time in the USAF.

Thanks,
Len

I was a aircraft weapons mechanic for two enlistments(1966-1974)Worked on F-105B's,D's&F's,F-106 A&B's and F-4C,D,E,&G models.

I was in the weapons release shop and flightline repair, so I got real good at aircraft electrical troubleshooting.

Just wanted to reply that I found my problem. My dyna green 3 ohm coils are both bad. The primaries both measure good at 3.2 ohms but the 1-4 secondary measures 51k ohms and the 2-3 secondary is open. I'm pretty sure the secondaries should both read around 14k ohms. I checked both the dyna modules and they seem to be ok. The thing that was misleading me was the fact that the bike would start right up and idle ok. Off idle it started to miss and as the rpm's increased it sounded like it was only firing on two cylinders. The thing that makes me mad is that I'm pretty sure I did this to myself as the last time I checked the compression I must have forgotten to remove the wire that powers the coils. This all started because my number 3 plug was black and I found a float level to high but decided to check the compression to. Also, when I first noticed it was missing I revved it way up to try and clean it out and blew the baffle out of my 20 year old Jardine header. So I spent $330 on a Vance and Hines and now will have to spend another $125 on coils. Oh well, live and learn.

Are the coils too old to be covered by a Dyna warrenty? I wonder how a set of Accel coils would work with the Dyna "S" system.

Mfolks do you know what the output voltage is on the Accel Super Coils? They have a lot of info on their site but I can't find the out put voltage. They are listed as 3.0 Ohm coils.

Dyna Green coils are supposed to have 35,000 volts as output, I'd imagine the Accel coils being pretty close.

I'll check the Accel website and check back....

No eBay APP ID and/or Cert ID defined in Kunena configurationJust Bought a set as I was asking:

380265247932

I looked around Accel's website,nothing listed as output voltage, probably sending them a E-mail to find out would be the best way.....