KZ650 2-3 coil cutting out after warming up.

Hello, I 'm having an issue that is really getting under my skin. I have a 1981 KZ650 H CSR that i bought last year. It ran great and then developed an issue like it was running out of fuel. I chalked it up to poor carb maintenance. So i built the bike over the winter and took it out for a ride. Rode great for a few days them boom, the issue returned with a vengeance!! The #2-3 coil was not firing the plugs after the engine would warm up, and headlight bulb was blowen. I pulled the boot off the spark plug and nothing. I found that the volt regulator had checked out. The volts were all over the place and spiking to 19v at idle. Just before it did this the bike would cut out the 2 cyls. I replaced the voltage regulator with a new one and OHM'd the Dayna oils. 3.0ohm on the dot. So i rode it for about 10 min with no issues. turned it off and started it again and boom no spark on the 2-3 coil again. Swapped coil out for a stock one and as soon as the engine warmed up same issue. I'm look for some advice on where to go from here. Is the stator the culprit? are they set up to have the slow and high speed winding in them like a Honda? Ant help would be greatly appreciated.

Since it's staying w 2-3, I guess do the igniter & pulsing coil checks outlined in the manual.
Also, make sure the battery is good. And I guess the new R/R checks out fine?
Just curious, what voltage regulator did you get? Thanks.

Yes the Voltage regulator is now spot on with the new one it was from RM stator on line. I have had good luck with that company in the past I will check the Pulsing coil as soon as i can find the OHMs it should be at. I wasn't sure if the Pulsing coils were part of the stator as they are in a Honda. Ill check it out and go from there.

You should probably get a manual too. On most KZ's, the stator is just a simple 3-phase or 1-phase set of windings... no funny stuff like on some Hondas. The smaller, rare KZ's, like the 200/250 single and 250/305 twins may have some ignition related windings in the stator area.

The 81 650 has a 3-phase alternator. The pulsing coil is under the right side engine cover (opposite side from the stator). The igniter is kinda hidden behind/below the fuse box. The pulsing coil & igniter connecters are under the tool case.

KZ Hardtail wrote: Hello, I 'm having an issue that is really getting under my skin. I have a 1981 KZ650 H CSR that i bought last year. It ran great and then developed an issue like it was running out of fuel. I chalked it up to poor carb maintenance. So i built the bike over the winter and took it out for a ride. Rode great for a few days them boom, the issue returned with a vengeance!! The #2-3 coil was not firing the plugs after the engine would warm up, and headlight bulb was blowen. I pulled the boot off the spark plug and nothing. I found that the volt regulator had checked out. The volts were all over the place and spiking to 19v at idle. Just before it did this the bike would cut out the 2 cyls. I replaced the voltage regulator with a new one and OHM'd the Dayna oils. 3.0ohm on the dot. .

I should post this on a sticky:

YOU CAN NOT RELIABLY BENCH TEST A COIL WITH AN OHM METER


A coil is actually a high voltage flyback transformer. The #1 failure mode on any HV transformer is arc over on the high voltage (secondary) windings as the insulation fails with age.

Poor running at warm temp is the most common failure mode of a bad coil. It will test out as good with an Ohm meter. If you have a HV tester, you might be able to pick up the failure but might not since it may be arcing between windings.

Swapped coil out for a stock one and as soon as the engine warmed up same issue.

If you are SURE the coil you swapped in is good, that means the ignition is bad. However: if it is an old coil, it could be bad too.

Ok great!!! Thank for all the info. Tested the pickup / pulsar coil and tested good. Hit it with a heat gun for a few seconds and Bam! No good! I ordered a replacement from Z1 enterprises and their Dyna system seems simple and looses the igniter box. Hope she runs like she did when done.