Weak Spark & Dyna trouble

Here I am, again. New troubles. Remedied my old problem: dyna s headache
81 kz750 w/Dyna S & green 3 ohm coils.

She ran just fine for 2 weeks, but now I have weak spark on cylinders 1&4. I CAN start & ride it, but at low RPMs it will just cut out and die. Revs fine over 3500 rpms. Coils have plenty of voltage coming in thanks to wiredgeorge's mod. Both coils read 3.5 ohms too.

I'm thinking the coil is just about shot? What do you think?

Contact Dyna and see what they say about the ignition coils. Have you looked here?

Ohm Checking Pickup(Pulsing) Coils

The pickup coils on the Kawasaki’s with the factory supplied electronic ignition can sometimes fail or become intermittent due to heat and vibration.

1.Trace back from where the pick up coils are mounted,(under a right side CD sized cover) locate and disconnect a small 4 pin connector. Using a multi-meter set on OHMS and range of 2K, check between the BLUE and BLACK wires(#1 and #4 sparkplug wires) for between 360- 540 OHMS.

2.For #2 and #3 sparkplugs the wire colors will be YELLOW and RED, again 360-540 OHMS. The 550’s,650’s & 750’s may be backwards to the Z1’s,Kz900’s,Kz1000’s & Kz1100’s.

3.If the pickup coils are suspect of failing due to heat, they can be stressed using a hair dryer without the need of the engine running.

4.A replacement set of pickup coils might be obtained from a dealer who serviced the police Kawasaki’s.

5. If replacement pickup coils are not available, your next choice would be to order a Dyna “S” electronic ignition system from www.z1enterprises.com It replaces the IC igniter with a smaller module located where the mechanical ignition advancer was mounted.

6. Checking with Kawasaki.com website has determined that the Pick up(pulsing) coils are available . The pulsing coil # is 59026-1133 and replaces the older # 1002, 1012 which were used from the MKII motors until the 2005 P24.

7.Check the small 4 pin connector that the pickup coils connect to for corrosion/loose pins too.

"Coil Mod".... :whistle:
One of the issues with the coil mod concept. Sure, 12Vdc plus to coils no doubt in most cases but rest of electrical system still suffering (under voltage) due to electrical connections/ignition switch/charging system etc....

Assumption on my part but most likely reason people install the coil mod in the first place is due to inadequate power being supplied to the coils thus fouled/carbon plugs...

What's the the DC voltage to the Dyna ignition plate?
Engine case/frame ideally grounded?
Dyna plate power feed soldered?
Dyna Static & Dynamic adjustments/test to spec?

First thought where when increasing RPM, voltage rises as expected. At low/idle rpm voltage decreases most likely under spec'd dc voltage... Possibly charging system component failures but with out voltage measurements, know way to say accurately..

Just assumptions where at this point in time, out the the DVM/volt meter for some measurements...

Your manual should provide the test/measurements for your charging system verification...

I tested the Dyna S per the instructions I found online, and they tested out OK.
Primary resistance of coils tested Ok too. 3.5 ohms, I believe.
I was unable to get a secondary resistance reading from either coil. Don't know if this has something to do with my meter. Tried with plug wires on & off, but still got no reading.
And Old Man Rock,
I Also plugged in a spare(brand new) regulator, with no change whatsoever. The engine ground is tight. And yes, I soldered all connections when I installed the coil mod.

Could this be a dirty carb issue, perhaps?

Buddy gave me a coil from an old Yamaha, and she fired right up.. :lol: