TOPIC:

Hi all, picked up this gem for a song a couple of weeks ago and am slowly working on getting it running. 1981 KZ750. Here are the deets:

• new battery freshly charged
• no spark on any of the plugs; I am inserting a plug into the cap and grounding it while spinning the engine over
• ~10 volts at each of the coils
• wires and connections all seem to be in good shape from the pickup to the ignitor to the coils; I have unplugged and re-seated all the connections
• pickups look clean and I pulled, dissembled and cleaned the advance and the rest of the goodies on the right side
• check resistance on the 4 wire bundle coming from the ignitor and it reads 450ohms which seems to be correct

Just found this post and will also be doing the other resistance tests, but anything else I should be looking for, or could be missing?

photos.app.goo.gl/xTiM6T8oTvFV65teA

Is the 10v at the coils with the engine static or cranking? If when cranking that's ok, if with ign on and engine static that is a significant volt drop which will dip below 8v when cranking !!
Have you measured the coil resistance (2-4 ohms on the primary dependent on coils, 10-15k Ohms on the secondary)
You can also connect an LED across the coil terminals (polarity sensitive) you will see the LED pulse when cranking if the igniter and pick ups are working

Lumbee
I had to delete your last post .
It came out with  nothing but code 
Read our about the site  section on how to post pictures and try again 
Dave

OK, here are the numbers I got. The only out of range number I got was the black/yellow <> yellow/red; so would we consider the unit bad? Also, I made note of the coil resistance at the bottom, those appear to be in range.

Also, I saw some talk of being sure the black/yellow are is grounded. I am not seeing that when testing...it reads open. Should the ignitor unit be grounded to the frame?

 

I would not chuck the ignitor based on those figures. At least not yet. Twenty years ago I was almost certain my ignitor was faulty. It wasnt and 20 years later its still working.
a few suggestions:

Wookie58's question about coil voltage is a good one and an answer would help.

If not done already go to the articles tab above, Select Service Manuals and download the one for the  gpz750. It covers your model and has test for the pulse coils (ignition pickups) and other electrical components. Select the Filebase tab and search for a wiring diagram. Z750 is the EU kz750

If you want to test coil resistance properly then unscrew the little black collars which hold tthe spark plus wires in the coil and pull them out. Dont worry, they go back in.  With these wires out you can get accurate resistance measurements. 
you can also check the spark plug wires for continuity. Spark plug caps may have built in resistors also and can fail. If spark plug wires are 40 years old then they are probably rock hard and may have corroded internally.

The Black/yellow wire at the ignitor is the ground wire and shoulconnect to a black/yellow which runs the length of the wiring harness. See wiring diagram

Also. What exactky do you mean by 460 @2000 etc handwritten on the pic in your post?

good luck



 

Meter on DC V
ignition key on
kill switch set to "run"

Black meter probe on negative battery post
Red meter probe on Black/Yellow wire close as possible to igniter
Reading should be as close to 0.0V as possible.
Anything higher than 0.5V is an issue.

Move the
Black probe to the positive battery post
Red probe to the red(yellow/red) wire going into the igniter(close as possible to the igniter)
Reading should be close to 0.0V as well.

Move the Red probe to the red wire at each coil.
Reading should be as close to 0.0V as well.


Turn off bike

These measurements tell you the quality of the wire connections back to the battery.
Anything higher than 0.5V indicates too much resistance along those specific circuits.
Those circuits being: battery to igniter and battery to each coil
But the bike must be "on" to make these tests.

Focusing on the coils I am getting resistance of 2.4 and 1.9 (@2k) when measuring across the electrical connectors. However, I am getting nothing when reading between two holes for the plug wires. Wonder if I am doing something wrong. Been messing with old motorcycles for a long time and NEVER actually seen a bad coil...much less two. I tried all the ohms settings on my multimeter and not getting any readings.

Regarding Wookies questions...I'm getting 10.98 and 11.02v with the ignition on and it drops to around 10 when cranking over, so I'm thinking that's OK.

OK, nevermind, after more tinkering I got a reading at the 20k setting on my multimeter...13.2 and 11.4 across where the wires go into the coil, so those seem to be good.

I did pull the advance and pickups apart and clean all of that up and put it back together. The advance was rusted solid (no movement), but I pulled it apart and cleaned and greased it so it snaps back nicely now. Any hooter, wondering if I did put something back together right there. Does anything look amiss below? As I said, the resistance tests pass for the pickups. What is the best way to get if a pickup is making it up to the coil? Wookie mentioned a test light between the two terminals that attach to the coil?

Not a test light (unless it's LED) connect an LED across the coil terminals and crank the motor, if the igniter is working the LED will pulse with the trigger pulses on the ground side of the coils
PS: voltage and resistance readings for the coils look good

Ok, I feel like I'm making progress! Actually saw spark on the plugs today 

JR, good call on downloading the GPZ750 manual. I found this test procedure and when through it and indeed, I laid eyes on spark on all the plugs. So, this is telling me the issue is with the pickups not sending a signal. I did resistance tests on the pickups and they passed. Is there a way I can force the pickups to fire if I touch a ground wire to the pick up lead should the points fire?

Exposed copper wire conductor here is not good.
I suggest adding epoxy / JB Weld right there to prevent vibration from fatiguing the joint, which is buried inside the plastic...
Mine looked exactly like that... before it failed...

My 2c....



H.