1984 GPz750 - misfiring during warming up

you need to get a junior hacksaw and cut it open then peel the top plastic away from circuit board, but not till you have checked the side stand switch by removing the wires from switch & splicing together. there are a lot of igniter boxes that will work (if yours is feked) RX1000 would be my go to but GT550 upwards will probably do or any 21119 prefix one, you can go with manual advance/retard option with loads of after market options once you identify its the igniter as you seem to think.

rangeroy wrote:

you need to get a junior hacksaw and cut it open then peel the top plastic away from circuit board, but not till you have checked the side stand switch by removing the wires from switch & splicing together. there are a lot of igniter boxes that will work (if yours is feked) RX1000 would be my go to but GT550 upwards will probably do or any 21119 prefix one, you can go with manual advance/retard option with loads of after market options once you identify its the igniter as you seem to think.

 

Not to hijack but I am curious about this procedure as I have a circuit boards with the epoxy on it. Wouldn't using a hacksaw damage the circuit boards if not careful? If you have any documentation or could redirect me to a thread, id be very interested.

get yourself a login on the 750 turbo site & look for fast ferrets post in how to section, all will become clear

Your negative wire going to the erratic coil may have a short to ground or a break in it if you can move it and the led stays on.
 
This will depend on the postion of the ignition rotor in relation to the pickup for that coil. 

I seem to recall loudhvx mentioning that some modules don't send a ground to the coil unless the module sees an rpm signal. This will keep the coils from overheating.

I would have to look at loudhvx's notes and at your service manual.

What is the resistance of your coils??

Can you send a photo of your pickup coils?




 

F64 wrote:

What is the resistance of your coils??

Can you send a photo of your pickup coils?

 

Th coils have 2.3 Ohms / 11.4 kOhms primary and sec. resistance.

For what my ignition pick up coil system looks like, please see the picture in my following post.

 

When reading about the Ignition system in the Factory Service Manual, it struck me that the built-in safety circuits that prevents one from starting the engine in gear, or specifically with the side stand down actually don't work in my bike. That may be the reason my attempt at shorting the black/white wire from the ICU to ground didn't result in anything. So I've decided to skip the splicing together exercise of the leads going to the side stand switch. 

Contrary to what the FSM says,  

 

 . . . I can start the engine with the side stand down. I cannot tell why, perhaps due to a previous owner having modified the wiring loom, or (?) replaced original components with non-standard ones? 

This is what the ignition pick up coil system looks like under the right side crankcase cover: 

 

As far as I can tell, no apparent faults, like chafed wires or loose connections. However, two (or rather three) things struck me.
1) although the wires from the ICU to the four pin block connector match the colours in the wiring loom diagram, one of those that goes from the connector block to the pick-up coils doesn't. The Red/white wire should connect to another Red/white one, but I see a Black/white wire going to the front-most pickup coil instead of a Red/white one.
Since 2) I can see that a previous caretaker has left his marks on the three cross-headed screws holding the coil supporting frame to the crankcase, perhaps a replacement pick-up assembly has been fitted???
(And 3, the same ham-fisted "mechanic" that stripped the threads holding the cyl.head cover onto the cyl.head has destroyed/stripped the threads holding the right side c.case cover in place) 

This is what the 'junction box' / fuse/relay holder looks like. The FSM (page 371, illustration N134) seems to suggest there are four relays on it, one being the starter circuit relay which on my bike hangs on frame tabs beside the 'junction box'. And I can only see one set of diodes instead of two, as the FSM shows. 

 

It should start with the stand down, does it continue to run if you select first gear and let the clutch out while the stand is down?

Wookie58 wrote:

It should start with the stand down, does it continue to run if you select first gear and let the clutch out while the stand is down?

Good point wrt test procedure, @Wookie58. 

1) Starting engine on centre stand, pulling clutch and selecting 1st gear, releasing clutch lever, engine still runs. Flipping  side stand down => engine cuts out.  

2) Starting engine on centre stand, with side stand down, pulling clutch and selecting 1st gear, engine still runs. Letting out clutch lever => engine cuts out. 

So the designed "safety system" does work.

When I carried out the above testing just now, the engine had failed to start at > 10 attempts since yesterday, with the ICU lying undisturbed under the seat. Now I lifted up the ICU rotated it one turn around the wires going into the block connector, and rested it 'upside down' behind the battery. Then the engine started on cylinders 2 & 3, running rough, but long enough to do test # 1. 

Before test # 2 I fiddled the wires going in to the ICU a bit more (which also included moving the ICU), and then the engine started immediately on all four. 

You may have a bad solder joint on your ICU.
or
bad wire leading to the ICU

You may just re-solder the pin connections on the circuit board.
Also look for any bad circuit traces that may have lifted or broken.

Double-check your connector into the ICU.
There may be a pin or pins that are not fitting snug in the connector

 

F64 wrote:

You may have a bad solder joint on your ICU.
or bad wire leading to the ICU

You may just re-solder the pin connections on the circuit board.
Also look for any bad circuit traces that may have lifted or broken.

Double-check your connector into the ICU.
There may be a pin or pins that are not fitting snug in the connector

 

Spot on with your diagnosis there, @F64   (but that was what I also suspected, from the beginning)

BTW, when you mention "circuit board", I take you mean that in the ICU, and not the Junction box circuit board? 

 = = = = = = =

Anyhow, time for another update . . . . 

Looking for poor connections in the wiring loom, I managed to pull out the female connectors from the block connector that is plugged into the ICU. For this I used a purpose made 'tang' to release the retaining barbs. Upon examination, The crimping looked spotless, but I found most of the female connectors to be very loose. So they were bent 'inwards' with a pair of pliars, and checked for tight fitting on one of the male connector pins. 

 

With the connector back together, and plugged in, I managed to start the engine immediately, on the button. And flexing the wires back and forth had no effect on the running of the engine. So that's one problem sorted. 

Then it was time for a test run. Starting OK, riding nicely a couple of km, when there was three brief misfires (running on the left coil, since the tachometer needle stayed put). After that it ran OK for around 15 km, when I took a break, and turned off the engine. After around 10 minutes it started very reluctantly, running on either coil. For 5-6 km it struggled to run on more than one coil, and cut out completely several times. When I had to restart the engine, after a minute or two, it started generally on all four, then quickly fired only one coil, then the other (tach needle sometimes dropping to zero, or remaining at normal rev indication, but also peaking briefly up to 5-6 kRPM when the engine was running at around 2), until it died. This went on and on, until the engine suddenly decided to run without any misfires at all until I came back home. 

Since that test run I've been looking for alternatives for my ICU. CMSNL list one new for around 390 Euros, plus shipping, tax and custom clearance fees. Several are offered on eBay for between 100 - 150 Euros (again + + +), and may be as dodgy as my own. A Czech company called Ignitech make several varieties of ICUs, one that should work in my bike ( www.ignitech.cz/zdroj/en/vyrobky/tci/man...wasaki%20GPZ1100.doc ) would be around 150 Euro (+ + +). And then there is the DIY alternative designed my inmate @loudhvx that @F64 links to in his signature line. The Wells model DR100 ignition modules seem not to be available anywhere, but I found that some Chinese offer what they claim are replacements for the ones used in eighties V8 Chevrolets . . . They look similar (which they are good at), but with a lowish price tag at 10-15 USD, with free international shipping, I've placed an order for two. 

Many moons ago I built an ignition amplifier from a kit sold by Velleman, that has worked nicely in one of my (even twin plugged) airheads, so I know which ends of soldering irons that do what. If it were not for the BMW has a manual advance unit, I could have tried my Velleman amplifier in my GPz . . . (perhaps - ?)

hmmmmm
i'm not totally convinced it is spark related.
It could be fuel or air. (and looks like there may be an evap system on this bike)

How long have you owned this bike?

When did it start acting this way?

 

F64 wrote:

hmmmmm  i'm not totally convinced it is spark related.
It could be fuel or air. (and looks like there may be an evap system on this bike)

How long have you owned this bike?

When did it start acting this way?
 

Evap system - just to make sure, this is what was fitted to some US (Californian) bikes, illustrated here? :

 

I haven't seen any of that. Especially not #16164 or 16165, and I cannot remember seeing the additional tap under the fuel tank when taking it apart to fix the fuel gauge. What did you notice that rose your suspicion? 

The frame number doesn't begin with the letters listed for C / U models, i.e. JKAZXDA1-, but ZX750.

I've had it nearly five years, but it has mostly been an ongoing garage project, going over most of what wears out.  The misfiring has been there for at least four years, but initially not bad enough to cause any problems with riding it. .