TOPIC:

Hi Guys,
I have a problem with my 1981 kz750 4cylinder, and hoping someone could help me out. Alright, I just got the bike running after cleaning the tank and the carbs, changing the spark plugs and the wires. The problem is I loose spark on #2, #3 cylinders, but this only happens after its been running for 15mins...(engine is fully warm)... and i shut it off, then when i go and start it up again, the coil to #2, #3, goes dead. But it starts to working again after sitting for about an hour and a half. I noticed that if i take the black(-) coil wire from the #1, #4 coil, and hook it where the green(-) coil wire goes for #2,#3, I get spark again to #2,#3.? So I tracked the green(-) coil wire down and there wasn't anything wrong with it, but I rewired it anyways. I got spark to all four cylinders after I replaced the green wire, and it ran great again. Then I took it for a ride to the store...(ran fine)...went in got my stuff and came back out...Started the bike and once again it was running on 2 cylinders again. If anybody can help me,I would be very greatful.
Thanks

Well Hello there.... You ,must have got lost in the MAW

I'm not 100% familiar with wether the 81 750's had points or elec. ignition with an ignighter box..?

I think its the elec. ignition... sounds like your half way to finding out the issue on your own.

Be sure to check that the coils are recieving proper voltage when hot. Just with ignition on (bike not running), the voltage across the coil inputs should be very close to battery voltage.

If when coil goes dead you change input wires/spark wires, and problem moves to other coil, then it is the pickups or the ignighter box (unlikely, but possible).

If same coil stays dead, then coil is the issue.

You can test the pickups with an ohm meter, and i believe they should be between 300-600 ohms, if not then bad.

GL!



This will bump things and get some more answers...

I wrote this for the bigger 4's, but it should apply for your bike too:

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.

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.


Ignition Coil Primary And Secondary Wiring

Ignition coils on the 80’s Kz1000,Kz1100’s and Gpz1100’s are wired the same, that is as you sit on the bike, the LEFT ignition coil primary(small wires) are two wires, RED and BLACK. The secondary (or sparkplug wires) go to #1 and #4 sparkplugs.

The cylinders are numbered left to right as you sit on the seat; #1,#2,#3, and #4.

For the RIGHT ignition coil, the primary wires, again are two wires, RED and GREEN, with the secondary going to #2 and #3.

The RED wire gets it’s voltage from the run/stop switch on the right handlebar switch pod.

The BLACK and GREEN wires connect to the IC Igniter(if the bike has the Kawasaki supplied electronic ignition) it actually gives the coils their grounds to fire the sparkplugs.

Primary(small wires) side of the coils will read between 1.8 to 3.0 ohms.

Secondary(sparkplug wire ports)side of the coil will read between 10.4K to 15.6K ohms.

To stress the ignition coils, take a hair dryer, heat the coils and see if the ohm readings change from cold to hot . If they do, it’s time to buy new coils.

Keep in mind, the wiring is reversed for the 550’s 650‘s and 750‘s, that is the RIGHT coil primary will be two wires, RED and BLACK with the secondary(sparkplugs) going to #1 and #4.

The LEFT coils primary wiring would be again two wires, RED and GREEN, with the secondary(sparkplugs) going to #2 and #3.

These engines have what is known as a “Wasted Spark” that is, a sparkplug will fire during an exhaust stroke. It does no damage and many other motorcycle engines have this design.

Well Thanks Guys,
I try some of this and see how it turns out.
Its been one thing after another with this bike.

kzcafe750_24 wrote:

Its been one thing after another with this bike.

This is not going to change

Ya, That is something I am too used to...But for buying the bike for only $300 in great shape I guess I shouldn't complain. Oh and I did some sanding on the contacts for the coil and 4 pin harness, and its been running great sooo...far...