Ignition system

Ran across an article on ignition problems on older bikes and it made sense. As a bike ages, like my 40 year old Z1, the wires, contacts both kill switch and ignition switch will ether have more resistance, the wires with age or weak contacts. After going to the coils to solve the problem and finding nothing wrong, I was stumped. The writer talked about installing a relay, one you can find at OR or AZ for 6 or$7, Run the switching terminal + from the kill switch, the hot wire gong to the coils, a ground of course, a direct wire to a tap after the fuse block, then through the relay to the coils. Simple. I have a mile and a half grade about 3% where I notice a lack of power whatever the reason. After I installed my new relay system, I hit the grade. At 55 in fifth I rolled it on an noticed the difference right away. Here I was planning to buy some Dyna coils but now I can spend that money on more important things, valves, valve springs and seals. I've been buying the parts on Ebay a little at a time. Almost there.
Steve

Do a search for "coil mod" and you will find this topic covered ad nauseum. It isn't necessary, it's a band aid to avoid fixing actual problems (like a bad ignition switch or corroded contacts). I currently ride a 1979 bike with 85k miles and the coil and wiring cranks like a champ.

Simple. I have a mile and a half grade about 3% where I notice a lack of power whatever the reason. After I installed my new relay system, I hit the grade. At 55 in fifth I rolled it on an noticed the difference right away

Well, OK. But:

After going to the coils to solve the problem and finding nothing wrong, I was stumped.

Did you replace the coils or just ohm the windings? Because old coils fail all the time and IMHO, should be replaced as a matter of maintenance. The "increased coil voltage" due to the relay may be flogging a bit of extra life into a dying coil (?)

This is the third complete overhaul I've done in to 40 years I've owned the bike. I changed the coils and have another set I bought on Ebay. I'll keep this set up and buy my new Dynas after I'm done with the engine. One thing at a time.
Thanks
Steve

As you have discovered using a relay to power the ignition circuit works just fine. You should also clean all of the connections and switches in the OEM harness and carry a spare relay. I've been using relays on my motorcycles for over 25 years and I've never had a problem.

You're right, The switch needs to be replaced, after all, it's only 40 years old. No I think I replaced it in the 90's. They do go bad. I re-crimped the switch contact plate just to keep it going for now. I'll have to replace the switch and seat lock as a pair. The kill switch was cracked, I repaired it but it needs to go too. And if once apon a time there was a dead short and I think in my case, the wire was cooked causing resistance in the wire. A spare relay is a good idea but if I get to the other things, I could use it for my extra lights. The old Z1's weren't set up for this.
Thanks
Steve

Hi I've gone through almost 100 threads looking for something that matches my issues and this is so far the closest I've found so here is my issue with some history of my trials and tribulations!
76 kz900 - main power wires throughout the majority of the bike are getting too hot! I have a new main harness new left and right control boxes new regulator/rectifier unit and a new dyna s ignition. Last march i did a partial tear down cleaned all plugs and contacts prior to all my new parts i just installed. It did have an older dyna s that burnt out last March riding to Daytona i lost power to 2 and 3. Needless to say the bike has sat since then and im slowly finding time to get it running. It will start and runs great but i can only run it for a few minutes before the main power wires start to warm up , i dont want to melt my new harness and such . Now it was heating up before i replaced all the stuff i mentioned earlier.
Now if i unplug the red wire coming from the dyna s rnunning to the split power connector to the coils it will not heat up but as soon as i plug it back in it gets hot won't blow the fuse but it did start to melt just a little bit at the ignition switch plug. One thing i haven't done is clean the ground wire from battery to engine? Im also using 7ohm dyna coils with nylon spacers. I do have some more wires to inspect i feel like i should see the smoking gun any day now. Im at a loss on this about to trailer it to the shop . Oh and did also purchase a relay switch but have not attempted to install it yet . Any ideas?
Thanks

Seven Ohm coils??? I thought the Dyna S uses 3 Ohm coils.

shawnp wrote: Hi I've gone through almost 100 threads looking for something that matches my issues and this is so far the closest I've found so here is my issue with some history of my trials and tribulations!

It sounds like you've narrowed it down to the ignition. Have you measured the primary resistance of the coils? The Dyna S requires coils that are 3 ohms or more. If you have a bad coil, that could be drawing too much current. You could also have a bad Dyna S, even if you just replaced it, but it would point to some other issue that is damaging it. A bad coil could damage the Dyna S.



If your coils measure above 3 ohms, then it would help to be able to measure current in the wires. Any chance you have a clamp on current meter? A proper one starts at about $150, but there are a bunch of cheap ones on Amazon. If they work at all they would probably be good enough to track this problem.

Something like this: www.amazon.com/dp/B0721MKXBC
But make sure it can measure DC current. Some will only measure AC current.

If you have a meter like this, the first thing is to figure out how much current you are pulling from the battery right now. Maybe you don't have a problem. Maybe the wires just get warm.

All of this can be measured by clipping the meter onto the red positive battery cable and looking at how much current is coming out of the battery.

With they key in the run position, leave the engine off, turn the headlight switch on, put the engine run/stop switch to run. I would expect it to be around 15 amps? Next turn the headlight switch off. It should drop to around 10 amps? Then turn the run/stop switch to stop. That should disconnect the ignition, and the current should drop to about 1 amp?

For one coil, Ohms law says 12 volts and 3 ohms should give you 4 amps. So for two coils, you have 8 amps. plus a bit more for gauge lights and whatever else. If you're under 10 with the headlight off, you may have a wire or connector issue, but the ignition isn't doing anything it shouldn't be doing.

For the rest of this leave the bike with the key on, run/stop on, headlight off.

If the battery is putting out much more than 10 amps, unplug the +12V power wire from the two coils. It should be a red/yellow wire. Also unplug the Dyna S power, which is the red wire in the Dyna cable.

Now the current should be pretty low, back to about 1 amp? If it's much higher, you have a problem, but it's not in the ignition.

Next plug +12V back in to the Dyna S (with coils still unplugged from the red/yellow power). The current shouldn't really change. If the current increases a lot you have a bad Dyna S.

Next plug one coil in to the red/yellow power wire. The current should go up, but not by more than more than about 4 amps. If it's more, that coil may be bad.

Plus the other coil in. It should go up by 4 more amps, and now you should still be under 10 amps total. If it's more, the second coil may be bad.