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Hi All,
I got my ZXR MOT'd the other day, brought it back home and it went onto 3 cylinders, and now it wont start.

It has a VERY weak spark, I've tried some spare coils and the spark is the same.

Should I buy a used CDI box and try that?

The rectifier wiring has been butchered, in the past as the connector isn’t the correct one, so some monkey has tie wrapped it together, one of the wires looks slightly burnt. Will the rectifier effect the spark or can I disconnect this to eliminate it from the problem?

Can someone give me some ideas….

I'm not clued up on wiring but my father was a auto electrician many years ago so he has more clue than me (but not with modern electronics) he's suggested making a new minimal loom as the bike is being converted to a trackday bike, but I'd like to get it running again.

Hows the battery?

Apparently new when I bought it, I had it on the Optimate when spinning it over without the plugs in.

Checked pickup coil on my multimeter (on highest Ohms setting) I think thats fine.

Disconnected rectifier as I dont see how it could be related to my problem (I'll solder and heatshrink the bad wiring at a later date)

Should have a 2nd hand CDI tomorrow in the post....

Struggling to think of anything else!

Someones MIG welded a bracket on the bike in the past, Im wondering if that could have damaged something??

Swapped CDI, nothings changed!

Check your earths too, theres one on top of the gearbox and one in front of the rear shock, black and yellow wires Failing that jump start off a car battery, plug gaps correct?

As it happens I had already thought to try that after fitting the other CDI today. I ran a couple of extra earth wires, one from the black/yellow on the CDI to the rear shock and another from the earth off the ignition switch to the rear shock too. I also bypassed the kill switch at the multiplug to rule out that. Still no improvement.
Plugs are CR9EK, gapped to 0.8mm

I'll try off the car tomorrow, the batterys showing 12.0 when cranking over without plugs in, perhaps the systems dropping below 12?

Not 100% sure on that, from memory you should be seeing at least 14v with the engine at 4000rpm, but since its not running i dont know. An optimate wont keep it properly charged either, youll need a proper charger for that. The battery could be new, but could be a pants battery.

none of the above will make any difference if the earth to the engine itself isnt very good

run an earth from the crankcase to the neg terminal of the battery.

12v while cranking should be fine, should be 14 ish @ idle once running

ah yes, I've read what you said now about the earths. Crankcase is a must, most important bit.

I cant see a crankcase earth on mine, Where abouts will be it located? I've run a wire from one of the sump bolts, I've given the plugs a good clean, but the spark is still weak.

Thought I would stick them back in and try it and it does run, but Im not happy with how weak the spark is. Its very hard to see in daylight (not just me expecting it to be better).
The bike was also running on 3 cylinders for a good while but this cleared up when I took it up the road

atreyu wrote:I cant see a crankcase earth on mine, Where abouts will be it located?

runs from battery negative to a bolt on top of the crankcase near the big breather pipe that links to the airbox.