cylinder 1 and 4 no spark

i have a 1981 kz750-h2. getting spark to cylinders 2 and 3. but no spark to cylinders 1 and 4. i looked on the wiring diagram and it shows 2 seperate ignitions coils one for cylinders 2 and 3, and one for cylinders 1 and 4. i checked voltage on (2 and 3 ignition coil) this one is operating correctly it has 12 volts on each connection. on ignition coil 1 and 4 i only have 12 volts on the red wire it also looks like both of these coils from the wiring diagram share the red wire. Im still missing 12 volts on the black wire. i tested back to the 4 pin connection coming out of the igniter and still don't have 12 volts to the black wire.


Does this mean its a bad igniter or something else?. also what should the voltage be coming into the igniter?...on the smaller 4 pin connection.?..what should the voltage be?


and also i bought the bike form a guy and it has a 8 ah battery. and i noticed on the wiring diagram it calls for a 12 ah battery. what kind of problems could this cause?

The IC Igniter actually gives the ignition coils their grounds firing the sparkplugs.

If you've tested the igniter and it is bad, contact "Loudhvx" and look at his igniter substitue he made using off the shelf GM electronic ignition modules.

He's used this for many years on his GPz550 with no problems.

My understanding on amp rating is how long the battery is rated to put out current for a lenght of time, in this case 8 amps an hour instead of 12.

If you want to get a higher capacity battery, the limitation will be in physical size.

Brettstl wrote:

...1981 kz750-h2. getting spark to cylinders 2 and 3. but no spark to cylinders 1 and 4. i looked on the wiring diagram and it shows 2 seperate ignitions coils one for cylinders 2 and 3, and one for cylinders 1 and 4. i checked voltage on (2 and 3 ignition coil) this one is operating correctly it has 12 volts on each connection. on ignition coil 1 and 4 i only have 12 volts on the red wire it also looks like both of these coils from the wiring diagram share the red wire. Im still missing 12 volts on the black wire. i tested back to the 4 pin connection coming out of the igniter and still don't have 12 volts to the black wire....

If not already done, would ohm-check the secondary loop on coil for cylinders 1/4, from plug cap to plug cap.
Am guessing to expect 18k~22k ohms. May also compare to secondary loop ohms on 2/3 coil.

Wouldn't be concerned about "missing" voltage on the black wire, as that depends on ignition rotor position.

Would also fit two brand new spark plugs in #1 and #4 caps, and visually observe for any spark while spinning over the engine (hold plug bases against head of engine while looking for spark).

Good Fortune!

[Click on image to enlarge view.]

i checked the ohms on the primary winding and cam up with about 2 on each ignition coil. i also checked secondary winding at the spark plug boots and came up with around 22. my meter leads would not reach all the way down into the spark plug boot so i unscrewed the boot and put the leads directly on the wire and came up with 11 ohms. both secondary winding came back with 11. so it seems like this is correct.


could this be a grounding problem since the igniter sends ground to fire the plugs?

Brettstl wrote:

...checked secondary winding at the spark plug boots...could this be a grounding problem since the igniter sends ground to fire the plugs?

What is secondary loop's ohm reading on the other #2/3 coil, and how does it compare to the secondary loop's ohm reading on the #1/4 coil?

It's important to include the plug wires and caps in the ohm measurement of the secondary loop, which could indicate a break in continuity due to the plug wires or caps.
That's one reason for also measuring from plug cap to plug cap.
Where plug wires are removable from the coil, may measure resistance in secondary wiring loop inside the coil by measuring ohms again at the coil output terminals.

Not understanding meter wire length issue, as disconnected #1/4 plug wires will allow the two plug caps to be held right next to each other.

If the igniter ground (black/yellow wire) is functioning okay for #2/3 coil, would expect it's also functioning okay for the #1/4 coil.

Good Fortune!

Be sure the ohmmeter is on the proper range setting.

The primary winding should be something like 3 ohms.

The secondary winding should be something like 14,000 ohms.

Good Fortune!

i meant the leads wernt long enough on my meter....after checking all the ohms on each side of the ignition coil they were all the same. after taking things apart a couple of times and visualy checking all four plugs began to spark. but after putting the plugs back in and trying to start it the spark went away for cylinders 1 and 4. Im thinking loose connection somewhere? and if an igntion coil or spark igniter is broken would it be intermitttin or would it be 100% broke.

The sparkplug caps contain a supression resistor that reduces the noise heard on radio's and tv's. Heat,age and vibration can cause these to fail.

I believe Z1 enterprises sells replacement caps, also if your sparkplug wires are replaceable,I'd suggest changing them too.The 7mm size should fit.

So your saying that when you pull the plugs out and ground them on the block they're sparking fine, but not when you screw them into the jugs?

Should be a nice fat blue spark. Also, are you getting a full 12v from the battery? Are you getting a full 12v at the coil?

thanks guys for all the help. i got it sorted out it was a bad connection down the line!!! fixed it and it started. Now i just gotta fix those darn leaky carb boots!!!

Brettstl wrote:

thanks guys for all the help. i got it sorted out it was a bad connection down the line!!! fixed it and it started. Now i just gotta fix those darn leaky carb boots!!!

carb boots --- does this refer to carb holders between carb and engine (in which leaks are basically non-fixable), OR airbox hoses (where leaks aren't quite as critical)?

Might consider starting a new thread in the carb category.

Good Fortune!