Any Wiring Wizards/Electrical Gurus Around?

Hey Gang. Need some electirical advice on my son's 1974 Kawasaki 125 enduro. It is a nice, 2 stroke single we restored this winter and had a few hours of running time before it died and refused to start. We pulled the plug and changed it, grounded it against the head and kicked over the motor. Nothing at all. Checked all connections and they were right and tight.

I am not very familiar with the electrical on these old bikes (we didn't touch any of the wiring during the resto job) but it appears to have a coil tucked under the tank on the frame downtube.

I have a couple of old coils from my Kz650. Is there a chance that one of these could be tried? The local bike shop is closed tomorrow (Sunday) and I would like to get the little guy back on the trails.

Any help or other suggestions would be appreciated.

Cheers-Colin Firth-Ontario Canada

The 650 coil is dual tower, so that's out, but how about an el cheapo automotive coil from the local discount auto parts store? That will probably work.

you could use it to test it the extra plug wire will fire at the same time

btchalice wrote:

you could use it to test it the extra plug wire will fire at the same time

If you do that, then the second plug wire "must" be grounded to the motor, otherwise the one going to the plug won't fire.
Think of the secondary side of the coils as a coil of wire (cause that's what it is) with two ends, one end is connected to one plug wire and the other end is connected to the other plug wire. In order to have a complete circuit (required in order to have electron flow) both plug wires must be connected. In a standard single tower automotive coil, one end of the secondary coil is grounded to the can, brought out to an external ground, or grounded internally.


Post edited by: steell, at: 2006/05/28 10:51

Standard coil:

THe high tension side should be shown as grounded to the shell, not the "return" which would go to the points.

As you said, he can use the 650 coil as long as he grounds one of the spark leads to the engine.

If it's a magneto ignition, or CDI ignition, the 650 coil may not work because it's impedance (not just resistance here) may be too high. Magnetos and CDI coils are very low impedance (and resistance).

Post edited by: loudhvx, at: 2006/05/30 00:21

The high tension side should be shown as grounded to the shell, not the "return" which would go to the points.

That is what I have always assumed, but I ran across the above pic on a website (several actually) and that got me to thinking that maybe I have been mistaken.
Next time I run across a single tower automotive coil I am going to measure the resistance between the secondary and the can and between the secondary and the primary.

Several problems with that diagram.

The points are supposed to be open during the spark, so the high-tension side, in that diagram, has no complete path. It would therefore complete the path by arcing the points... exactly what you don't want, because if the points are arcing, you would have no high-tension circuit. In other words it can't work. It would only melt the points.

Maybe I'm wrong, I haven't measured a single-post coil, but I don't see how.