TOPIC:

I know ive seen this posted some where on this site but i cant seem to find it.
Im getting 12 volts at my coils until i plug them in. After i plug them in the voltage drops to about 8v. What could be causing this?

not sure what you mean by plugging them in.

Voltage drop at the coils is simply a result of ohms law. You have a bad connection somewhere in the bike. That bad connection acts like a resistor. When the coils draw current, as they do in normal use, that current produces a voltage drop in the bad connection. You then see that voltage drop at the coils if you measure it.

The most likely places are the fuse holders, kill switch, and ignition switch. Look for discolored or melted wires in those areas.

jadkins91 wrote: . . . getting 12 volts at my coils until i plug them in. After i plug them in the voltage drops to about 8v. What could be causing this?

plug them in -- what does this mean?

getting 12 volts at my coils until i plug them in -- 12 volts measured where?

After i plug them in the voltage drops to about 8v -- 8v measured where?

It's the red or red/yellow wire from the harness that typically splits and feeds battery positive voltage to a primary terminal on each of the two ignition coils.

Measure the voltage at the plug from the harness before connecting it to the coil.
Ideally, the voltage (at the plug from the harness before connecting it to the coils) should match the voltage as measured at the positive battery post (terminal).

The following illustration for larger fours might be helpful.



Good Fortune!

Loud / Patton,

Thanks for the response. Here is a brief rundown of the past week.
- Low voltage at coils so i installed the wired george mod which I assume I had wired it wrong due to the points burning up.
- Bought new points and installed them . Adjusted gap and timing using the continuity method.
- Turned the key on and one of the main fuses blew.
- Noticed that 2 wires leading into the kill switch assembly were nicked and to be safe i installed the assembly from my 81kz750, bypassing the headlight switch.
-Turned the bike back on and all was good. Had ~12V at the yellow/red wire that feeds the coils until i connected the coils then the voltage dropped to around 7-8v.
- I then turned the bike off and back on and the same fuse blew.

I though I had it all figured out..really frustrating.

Hey guys last time I checked I was getting 12.17 to one and 12.19 to the other ....... plan on checking them again (and doing a little cleaning) and was wondering "whats" about the best you can expect to get. Was gonna start a new thread but thought it might be easier just to ask here. Thanks.

jadkins91 wrote: . . . Had ~12V at the yellow/red wire that feeds the coils until i connected the coils then the voltage dropped to around 7-8v. . . .

7-8v measured where?

Good Fortune!

At the yellow/red wire that feeds the coils.

KZB2 650 wrote: Hey guys last time I checked I was getting 12.17 to one and 12.19 to the other ....... plan on checking them again (and doing a little cleaning) and was wondering "whats" about the best you can expect to get. Was gonna start a new thread but thought it might be easier just to ask here. Thanks.

wondering "whats" about the best you can expect to get --- the best voltage you can expect to get at feed to the coil will be the same voltage as measured at the battery positive terminal/post.

In other words, whatever voltage the battery is capable of supplying travels through a path of wiring, fuses, connectors and switches before reaching the coil. It's possible that some of the voltage may be lost during its travel along the path, which results in less than full battery voltage actually reaching the coils.

Good Fortune!

jadkins91 wrote: At the yellow/red wire that feeds the coils.

What type of volt meter is being used on an already connected wire?



Good Fortune!

Patton,

I'm using a Fluke 323 Multi meter that i used when i was an electrician. I placed the black lead on the negative terminal and inserted the red lead up in the connector.

KZB2 650 wrote: ...was wondering "whats" about the best you can expect to get. ...

It will be near the battery voltage if the coils are not energized (drawing current) and there are no other loads like lights etc drawing current. But normally, when you power up the bike, there will be loads drawing current. Then ohms law takes effect and every wire that has current through it will have a slight voltage drop. Every connection or switch that has resistance will also have a small drop.
The biggest factor is really if the coils are "on" or not...that is, if the points are closed or not. With the points closed, the current draw will lower the voltage a bit more. The points on a Kz are such that there is a slight chance that both coils are on. Then the drop will be higher again.

With both coils off (all point open), then I'd say about 1/2 volt lower than the battery is doing pretty good. With one or both coils "on", I wouldn't be surprised if the drop was closer to 1 volt. This is with the black meter lead on the battery's negative post.

Regarding the bike in question, I would try to figure out the fuse-blowing issue. That is more worrying than the low voltage, but could also be the cause the low voltage.

I would do a close inspection of the harness, especially near the steering area. Does this bike still have wires inside the handlebars? That would be suspect if it does.