1984 GPz750 - misfiring during warming up

The big problem with using Lou's HEI module is that you need the mechanical advance and pickup coils from an older GPZ.
Your system has electronic advance control not mechanical.
But it is possible to (according to Lou) to fit a mechanical advance unit to your bike.

I think my HEI unit is close to 10 years old now.
I may have gotten an older NOS unit from ebay.

Ignitech does look good as you can dial in your advance using a computer.

kzrider.com/forum/4-electrical/611881-19...-igniter-unit#814689

just spit balling here

I'd like you to try something.

Ride the bike around and get it warm.
Get it back home and let it sit for 10 minutes.
Hopefully, it will be difficult to restart.
If it is, spray some starting fluid into the airbox and try to start it.
Does it fire up?

I'm wondering if your plugs are fouling when the bike is heat soaking.
It's weird that your bike is running ok....you shut it down..let it sit ......and it's hard to restart.

Oh, and here's a terrible idea I once had.
I hooked up a scooter's dc powered cdi box to my kz440. sorry Kettering
It didn't last long as I sheared the roll pin in my crankshaft for the ignition rotor.
The cdi has a built in advance so I had to disable my mechanical advance.
That's how I sheared my roll pin. 
The bike did sound much angrier with cdi when it was running.
I may hook it back up one day.
I used the stock pickups on the kz and bypassed the igniter. Basically, I just used the cdi, the coil, the pickup--no igniter.
Something like this
www.scooterworks.com/products/rdln-perfo...MGfR-A4ozmewhMpDi4ww
I'm not very smart sometimes.

 

I believe there is also a 4-pin connector for the pick-up coils - as the pick up wiring runs around the motor it will be subject to heat, as we know heat increases resistance so if that connector is "marginal" to begin with, as the engine heat increases the resistance, that may be a factor (the pick ups work on very small voltage)

F64 wrote:

The big problem with using Lou's HEI module is that you need the mechanical advance and pickup coils from an older GPZ.
Your system has electronic advance control not mechanical.
But it is possible to (according to Lou) to fit a mechanical advance unit to your bike.
 

Ooops - I obviously missed that point when reading about the HEI ignition setup for the 550. It wasn't mentioned that it was designed for an early GPz550, I think the later ('82-on?) versions have an analogous electronic advance similar to the one in my '84 GPz. When assembled, the HEI ignition device should at least show if my engine easily fires up on all four, and idles as it should.  

Good point about also checking the Igniter to coil pick-up leads, @Wookie58. I noticed that the Factory Service Manual specifies test reading values for both the IC Igniter and the pick-up coils, so I measured resistance readings for both units with my multi-meter. As shown in this table, some values were higher than specified, possibly since I didn't use the 'approved' Kawasaki test unit? In any case, the significance of those readings are for now unknown, especially since my intermittent fault most likely hasn't influenced the readings I got. Perhaps other ICUs in perfectly running bikes show the same differences, who knows until a large enough selection of them are tested. 

 

The FSM also gives an acceptable range of resistance values for the pick-up coils, 380-560 Ohms. I measured my rear pick-up coil circuit (Yellow and Black wires) to 460 Ohms, while the front one (YELLOW/black and Blue wires measured 890 Ohms. I didn't manage to get the male 4-way connector on the wires going to the pick-up coils apart, so cannot tell if the higher value for the front pick-up coil is due to corrosion at the 4-way plug crimping or at the coil itself. Identical Ohm readings were measured at the 10-way connector block at the ICU. The FSM says 'replace unit' if readings are outside the published acceptable range, but I'm not sure about the significance of this either, since my engine runs perfectly at times. 

Two more test runs carried out, the first hoping to get a repetition of the last one. Before I set off for run #1, I drained the fuel tank so I would run out of fuel, so I could compare known lack-of-fuel cutting out with what I take as ignition related cutting out. The engine started OK, on full choke (now getting chillier here, up at 60 deg. N), and suffered 4 to 5 brief "misfire/cutting out" events before running OK after 4-5 km (tachometer needle kept indicating engine RPM). After another 10 km the engine began stumbling, this time a bit more gradual, as a reluctance to rev from low RPMs (not the rough running seen when the taco needle went to zero, or temporarily peaked to about twice the engine RPM). Flipped the fuel gauge lever from ON to reserve, engine quickly reverted to run faultlessly. And ran OK all the way back home. Turned off engine, waited 5 and 10 minutes, engine started instantly on all four both times. So no chance to test the 'starting-fluid-in-airbox trick . Entertaining behaviour, n'est ce pas?
Test run #2 began as the previous, brief stumbling episodes w normal tachometer reading. Then, after a couple of km further down the road, brief stumbling episodes, this time with the tachometer needle dropping to zere, and up to double engine RPM before normal running continued. Turned around and got home without major problems. Waited 15 min, and then the engine only fired on two cylinders, ran rough. Waited another 10 min., no change (ie rough running on two cylinders. No effect of starting fluid sprayed into the airbox. Pushed the GPz back into the garage and left it to cool down. 3 hours later it fired up on all four . . .  

  

That one pick is way over spec - try checking pick resistance again when everything is hot

I had a bad ignition pickup years ago..
It would fail when the bike got hot.
Then it would be fine once it cooled down.

I found it eventually by heating it up with a hair dryer while i was watching an ohm meter.
When it would fail--it would open up completely.

You could also get a can of air(dust off).
Invert the can to freeze the pickup to see if that changes the resistance of the pickup.

I was also worrried about electrical noise interferance on the pickup wires as the signal is low voltage.
I changed my pickup wires to a shielded Tezfel wire.
The Tefzel also has a 150C heat rating.
Wookie, your mentioning of resistance changes with heat reminded me of this.

www.aircraftspruce.com/catalog/elpages/d...WV4rWShoCLkUQAvD_BwE

During the last few days I've focused on the ignition pick up coils (IPC), taking resistance measurements when cold and after a brief ride - most rides having included incidents with the ignition cutting out, usually with cylinders 1 and 4 (right coil, served by the black signal wire from the ICU) first, and then #2 and #3, with corresponding aberrant readings of the tachometer. 

I've confirmed the resistance readings of the IPCs when cold, at 460 Ohms for the rear IPC, and between 640 and 890 Ohms for the frontmost one - confirming that the latter reading is outside the acceptable range. 

When warm, the frontmost IPC returned a fairly consistent reading of 550, 580 and 570 Ohms. Rear one; 820, 870 and 890 Ohms, but often the latter readings were fluctuating wildly (300 - 1200 Ohms) before the meter needle settled down. To me, this makes me suspect the frontmost IPC as the major unit responsible for my ignition problems . . . 

I read @577nitro's thread "1981 GPZ550 Ignition Magnetic pickups weird failure, firing 60 degrees advanced" with interest, and also @Wookie58's "82 KZ100 Ltd" build thread, where he describes he used aftermarket GPZ900 IPCs, with a suitable resistor added in-line to provide an acceptable Ohm value for the ICU. 

Where did you get those IPCs from, @Wookie58? I've noted that Ignitech in addition to ICUs offer several individual IPCs, but none seem to be identical matches to the GPz750 ones. And the only shipment option they offer to Norway (outside the EU) is DHL, which charge more than the cost of two of their IPCs. 

OldRetroRider wrote:

Where did you get those IPCs from, @Wookie58? I've noted that Ignitech in addition to ICUs offer several individual IPCs, but none seem to be identical matches to the GPz750 ones. And the only shipment option they offer to Norway (outside the EU) is DHL, which charge more than the cost of two of their IPCs. 

The ones I have came from Ebay but I can't find them in my order history (been collecting parts for my build over 4 years) many of the Kawasaki's share the same style of pick-up (yours is the same as all the later 550's and 750's) I believe some of the part number differences are down to the mounting plate or grommet ?? you may be better trying to find some locally from another Kawa 550, 600, 750, 900 etc. If the physical dimensions are right you can use resistors to correct the total circuit value.