C25-coil fault but the coil isn't the problem? Pointy

Hi guys,
just touching the ton (off road of course) the other morning on a brisk ride, I got a bit concerned as the bike suddenly lost power and started sounding lump......
Pulled into a layby with the warning light on and the bike trying to run on one cylinder, did a quick check over then took a slow plod home in 'restricted 325cc single' mode.....

As I had previously had intermittent firing problems on the rear cylinder and changed the coil with a cheap replacement before finding the plug to be faulty, thought maybe the 'cheap' coil could have given up and with finding a C25 fault code, went back to the original coil (only had 1500 miles on it) confident it would sort it.

Disconnected the battery to clear the memory, fired it up and was still on one with the FI showing on the dash.
Got the C25 code on again so I'm guessing the FI system is still thinking there is a problem and cutting the cylinder.

My issue is, the coil is testing fine, so is the cap, so is the plug but when I remove the power supply to the coil, the bike runs on one cylinder (expected) but there is no FI warning and no power coming to the terminals that supply the coil (tested on the 10 volt scale).

I'd at least expect the FI warning to show without the coil connected but because it isn't, I also expect power to be coming into the coil (would understand no power with 'FI' as it will cut that cylinder).

Any ideas what the 'fault' could be?

Maybe a way to clear the memory (if diconnecting the battery doesn't do it) or bypass the fault protection system to make sure it isn't causing more of a problem by finding/remembering/making up a fault that isn't there?

Thanks in advance

[Bibio]

the ECU is not clever enough to have a limp mode.

is there anything else that you have done to the bike recently (mods, levers etc.etc) apart from the coil issue and possibly before?

might also help if you tell us what year and how many miles the bike has done.

Originally Posted by Bibio

the ECU is not clever enough to have a limp mode.

is there anything else that you have done to the bike recently (mods, levers etc.etc) apart from the coil issue and possibly before?

might also help if you tell us what year and how many miles the bike has done.

Hi buddy,
Haynes states:
'C25 - Rear Cylinder Ignition Coil - engine will run on other cylinder, ignition signal to cylinder 2 cut'

Nothing else done this year (or the last couple) other than putting the original plugs back in after a suspect iridium one seemed to be breaking down.

Bikes been fine for 40 miles since then (4 mile round trip to work a few times over a couple of weeks), not missed a beat but now firmly running on the front cylinder only.

2006 SK6, 1570 miles when it stopped running on two.

[Bibio]

sounds like another duff plug. get yerself a nice new set of plugs and stick those in. remember to take the nipple off the top of the plugs (if they have them) so just the threads are showing and push the plug cap down firmly with the little triangle on the rubber part pointing to the exhaust e.g. the rear one points towards the back and the front one points toward the front. another thing is if you pull on the HT wire instead of the cap it can snap the HT lead inside the cap.

[Red ones]

7 years, less than 1600 miles?

Originally Posted by Bibio

sounds like another duff plug. get yerself a nice new set of plugs and stick those in. remember to take the nipple off the top of the plugs (if they have them) so just the threads are showing and push the plug cap down firmly with the little triangle on the rubber part pointing to the exhaust e.g. the rear one points towards the back and the front one points toward the front. another thing is if you pull on the HT wire instead of the cap it can snap the HT lead inside the cap.

Tested the plug, cap and coil to check for an open circuit as they seemed the most obvious and easily changed.

I suppose the most obvious test would be a complete plug and coil swap from front to back, that should make it a C24 (front coil) fault if it's either of those.......

I'm looking at the fault possibly being further up the line as there is no power coming into the rear coil with the positive and negatives on the voltmeter and the bike running (on the front cylinder).

Originally Posted by Red ones

7 years, less than 1600 miles?

Yep, owned since new, got 900 mile in by the end of 2007 for it's first service and spent every year since promising to use it more but never getting it out more than 4 times a year.

Hoping a late start to this year would change that but not if it isn't going to keep running on two cylinders

[Bibio]

how many services has it had?

i would start with a new set of plugs m8. i very much doubt that its the coils.

if the bike has been sitting about check the connectors that are open to the elements then the ones that are not.

how fresh is the battery?

Originally Posted by Bibio

how many services has it had?

i would start with a new set of plugs m8. i very much doubt that its the coils.

if the bike has been sitting about check the connectors that are open to the elements then the ones that are not.

how fresh is the battery?

No service since the '1000 mile' service, the George White's I bought it from went tit's up a couple of years ago and although everything has aged whilst stored in the shed, never saw the point in servicing it if it hasn't gone anywhere.
My brother is an MOT tester and the old man has been on bike since long before I was born hence having a bit of mechanical knowledge.....

Haynes says 'faulty power supply for the ignition system' as a possible cause for C25 so digging under the airbox and disconnecting/applying vasoline/reconnecting all the connectors whilst under there is on the to-do list whilst swapping the plugs and coils to see if the fault changes cylinders...

Suppose putting the 'good' iridium plug into the rear cylinder and seeing if that cures it is an easy option and would answer the possible plugs thoughts....

Battery is good, been cycling on the Optimate and never spun slow although I must admit I've noticed the headlight are almost completely out when firing it into life (sparks into life just like the first day I bought it, just now it's on one cylinder)....

Thanks Bibio!

[Red ones]

I think the lights are supposed to go out on start up. Always have on my K5