odd ignition prob, ZXR750..update

[Tack]

my 1991 zxr750 track bike...I've got a track day tomorrow and I have developed this really odd ignition electrical problem.

Basically, you start the bike up it runs fine and then drops onto two cylinders...2 and 3 run but 1 and 4 drop out. Probably the coil you would guess but this is the second set of coils with exactly the same issue!

Thing about it is that it then comes good...runs fine, revs fine. then it will do it again...run it for a while and it clears and runs ok again???

You would think that if it was a coil or lead issue that it would be consistent...but tried another set of coils...another set of leads, another set of spark plugs.
Same thing! Behaves exactly the same.

I've shook wires, wiggled them..tapped things...dunno.

any guesses..thanks.

I've got a track day tomorrow and really would like to fix the problem so any help would be much appreciated.

[Strika]

CDI might be going mate? Got a spare one?

[Tack]

nah I haven't strika...bugger hey...have to suck and see


why only two cylinders though?? is it a dry solder or something inside the module??
thanks very much for your quick reply.

[jefflthomas]

i've got no idea but seeing as you're desperate....

any aftermarket electronics?...like a quick shift cut out or a rev limiter

[Strika]

nah I haven't strika...bugger hey...have to suck and see


why only two cylinders though?? is it a dry solder or something inside the module??
thanks very much for your quick reply.

Didn't have much to go on, figured you had checked everything else, so thought if you had a spare it might be worth swapping over to try. If changing coils doesn't alter which cylinders are dropping out, then it is suggestive of something prior to the coils in the chain of command! Hence, I thought CDI. But, I still maintain, that you have probably broken a smoke seal. Because as you well know with electrics, they work on smoke and once the smoke escapes, they don't work anymore. have you tested the smoke seals???

[Bogan]

If you find out what it is please please post it up here mine is doing exactly the same thing randomly, I'm not sure which cylinders but it could be the same as yours. Sometimes a sharp bash on the seat clears it making me think it's a loose connection/busted wire in the loom or something, and I'm going to pull the back half of it apart soon and clean all the connections, but if I had a targeted place to start that would be ace.

The only comfort for you may be knowing you're not alone?



Oh BTW mine started doing it after a tune at a local place, but it's been back there and he wasn't able to fix it . Have you done anything to yours lately?

But, I still maintain, that you have probably broken a smoke seal. Because as you well know with electrics, they work on smoke and once the smoke escapes, they don't work anymore. have you tested the smoke seals???

I know Kawasaki don't come with Lucas electrics but if it is the smoke maybe you should take a couple of bottles of this to track days...


Just top it up if you see it leaking during the day.

[Johnnie5]

have you actually checked that there is spark or lack of

do they run 1 or 2 hall effect trigger sensors ?

it quite possibly be a CDI fault , affected when hot

or could just be a bad wiring connector

[Tack]

have you actually checked that there is spark or lack of

do they run 1 or 2 hall effect trigger sensors ?

it quite possibly be a CDI fault , affected when hot

or could just be a bad wiring connector

yeah definitely no spark...pulled the plugs after fitting new ones...no carbon on 1 or 4...can even pull the leads on 1 and 4 and no affect on running..pull 2 or 3 and it stops..
I put plugs in the leads ...earthed the plug...turn it over...no spark...so I think I've done most possible checks

The bike has one hall affect sensor which sends the signal up the wire to the CDI box (ignitor?) which distributes the pulse to one of two coils...1 & 4 coil or 2 & 3 coil.

The problem is intermitant...I ran it at the track today and it ran fine most of the time...oddly turn 3 at QR it carried on 3 or 4 times...while in one 8 lap session there was not a hint of trouble!

Thanks for the replies...and strika there might be some smoke when I burn the bloody CDI unit..

[Johnnie5]

if there is 1 hall sensor then you can eliminate that

i would be looking for a wiring problem from cdi to coil

[Tack]

if there is 1 hall sensor then you can eliminate that

i would be looking for a wiring problem from cdi to coil

Yeah well I will check the whole thing but I find it unusual that when the bike is standing still, not moving, on stands and it running fine and all of a sudden it will drop out. I would expect a wiring issue to occur when it's moving or if once it drops out it would continue until you wiggled wires or plugs ...but it comes back all by itself.

The problem was initially that it would start run fine then drop cyls. Wait a while, start run fine then drop cyls again.

[Tack]

I removed the IC ignitor from the bike and got the multi meter out.

In the manual it has all the resistences for each circuit.

There are 6 pins on one side of the ignitor that go to the ignition coils etc and 4 on the other connector that recieve the signal from the pickup coil down on the crank.

Anyway after checking each circuit as per the book...the left 6 pin circuits doesn't make any sense what's so ever. The right 4 pins circuit checks out perfectly with the book.

I can only conclude that either the multi doesn't read the circuits properly or that the thing is stuffed.

So I pulled the thing apart and had a look inside.

looks melty!

088 edit.jpg (246.73 KiB) Viewed 3650 times

Nothing seems badly burnt, no capacitors have exploded or resistors have melted but there is definately a "I've been hot" smell about it.

So I dunno. Anyway I'm considering buying one of those dynatech units which supposedly allow timing adjustment.

Anyone used one or know what they're like.

[Johnnie5]

huh ?

look at that transister in the middle , its toasted

it is obviously breaking down as soon as it warms up a bit

[Tack]

huh ?

look at that transister in the middle , its toasted

it is obviously breaking down as soon as it warms up a bit

The point of the post was that I tested it, it didn't make any sense and I am going to replace it and I was intersted to see if anyone had anything to say re the dynatech.

[Strika]

Mate, I forgot what you are doing with this, track? Road? If you are roading it, just get another CDI. If you are tracking it, send it to Bert at Small Coil Rewinds in Geelong and see if he can both fix it and also modify the ignition curve and even the rev limit if you want. My 95 ZX6 ignitor was done by him. Cracking curve from 8-infinity. (It has no limiter)

[Tack]

Thanks Strika. It's for my ZXR750 which is a track only bike.

It's a bit of a difficult situation. The thing is that I have this other engine that supposedly an ex TKA engine. (Dunno if it is or not but if it's got more power then the boat anchor I've currently got then I don't care). The issue is that it's an earlier engine (eng no. ZXR750FE) which I understand came out of the 89 or 90 H1 or H2 ZXR750. It has been modified to fit into the J1 chassis.

I dunno if many people are aware but the J1 1991 ZXR750 bike was limited by Kawasaki to 100hp because there was some talk around the world that governments were going to restrict all bikes to this 100hp limit. That didn't happen but Kawasaki built the bike anyway! And I bought the stinkin' thing without knowing.

Thing is that at a track day I get blown to the weeds down the straights. I catch and pass guys out there on modern 1000cc bikes under brakes and thru corners and they just twist the throttle and pass me back on the straights. They pull 100 150 metres on me and I get em back under brakes and thru the corners which is a pain in the arse cause you don't know what the hell they're gunna do as you pass them and sometimes you nearly run into them because they just don't expect you. For example I'm doing 209km/h and hit the brakes at the 150metre mark on the back straight at Queensland raceway and tip into a 60km/h corner. These guys are braking before the 200
marker! I'm doing 209 and they're probably doing 120 as I pass them. That's fine, I don't have problem with them doing that but I'd just like to stay away from them, preferably ahead. Hence the reason for wanting to put this race engine in. Who knows it might be a dud in which case I might get a 900cc ZX9R engine and put that in.

There's no two ways about it but this engine I bought is a race engine. I am really interested to see what it goes like.

However, I don't know much about this race engine, what compression ratio it has, cam lift or duration or even what fuel it should run so I was a bit concerned about what sort of rev limit it should have and what sort of advance curve it should have. (thought it does have a modified advance rotor on it which I hope is the original race one)

The thing about this dynatech unit is that it has a fully adjustable advance and limit, different advance curves etc. etc.

http://www.dynaonline.com/skins/product ... dyna_2000/

However they don't make a rotor or pickup for the earlier engine.

But the rotors are identical on both engines and the 91 pickup will fit (the 89 engine coil pickup (hall sensor) wasn't on the engine when I bought it) and the 91 coil pickup, when fitted to the 89 engine, is approx 2 mm off centre and only just comes within contact range of the coil.

I've talked to the dynatech people about it and they reckon it's close and it might work but they don't really know if it's possible.

Anyway I'm gunna play around with it and see what I can do.