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I fired up my track day bike today only to find it firing on 2 cylinders, which is odd as it was running fine a couple of weeks ago. Charged battery and changed 2 middle plugs for new ones (2 & 3) and it misfired into running 3 cylinders. Swapped plugs 3 & 4 and it ran on 2 cylinders again. Swapped them back and changed 1 & 2 only to find it running on 2 cylinders again.

Plugs don't seem damp or covered in oil and I've had a spark from all of them. Anyone know what the problem might be? Coils aren't damp either and all connected properly. It's running a total loss system if makes a difference to any problem solving! Please help!

Bump - Still suffering! Help!

have you checked the earth straps are in good nick, what about the wiring to the coils?

if the original HT leads are still on then its possibly them.

How do I know if the HT leads are knackered? I've got a spark in all 4 plugs but maybe not enough spark? Do I test them with a multi meter?

oh well if they are all sparking they are ok probably, I was meaning that the lead ends could be badly connected as many originals seem to be after repeated services and etc.

Have you tried all new plugs?

make yourself a new HT lead up and swap them one by one checking for a GOOD bright spark.

u can check the resistance of each lead it tells u how to do it in the manual! if they are not correct then the bike will miss fire

Swapped the coils over after it failed to fire on 1 & 4 and it ran on all 4 cylinders Great news but bloody confusing! Swapped them back to original position and fired again on all 4 with a pop from the exhaust every now and then. Very odd but guess it was a dodgy connection somewhere.

Funny thing is, the tacho had been wired up prior to start of all this and it wasn't working but when I switched the coils over it was going backwards?! After I swapped them back to normal it was working at all. What wires could be wrong?

the wires are colour coded!

ratbag56 wrote:the wires are colour coded!

Er... Thanks for that!

But what could be wrong?

Went on a track day to test the ZXR400. Got it firing on all 4 cylinders after the routine swap of the coils and HT leads. As soon as I pulled away and put it into 2nd and the revs picked up it went back onto 2 cylinders.

Pulled into the pits and it fired back into all 4 . Went back out again and back onto 2 cylinders. What the hell is going on?!

Is there any way of testing the coils or HT leads? How do I do it? Is something wrong with the CDi unit? Please help!!

if you hold it at a constant rev's (say 9,000) dos it go back to 2 then?

if it dosnt do the above you must have a lose conection what only happens as the vibrations pick up!

It was kicking in and out of 2 & 4 cylinders down the backstraight and all corners, so vibrations would be plausable.

What wires should I check for loose connections?