Have I diagnosed this right?

[Mad Hatter]

Intermittent rough running and dead stop cut out every now and then, but restarts quickly enough, with a bit of rough running, then ok again. Feels like it’s down on power when it happens. It’s instant when it does it so it doesn’t feel like it’s fuel related. New digital bean can fitted months ago, carbs rebuilt months ago, ultrasonic cleaned and all new jets, set up bob on. New loom, new plugs and new plug leads. Timing bob on, valves bob on. Happens both hot and cold

I think it’s probably the coil, but could possibly be ignition unit, or dodgy kill switch.

Whadaya reckon, coil?

 

[2gses]

Intermittent rough running and dead stop cut out every now and then, but restarts quickly enough, with a bit of rough running, then ok again. Feels like it’s down on power when it happens. It’s instant when it does it so it doesn’t feel like it’s fuel related. New digital bean can fitted months ago, carbs rebuilt months ago, ultrasonic cleaned and all new jets, set up bob on. New loom, new plugs and new plug leads. Timing bob on, valves bob on. Happens both hot and cold

I think it’s probably the coil, but could possibly be ignition unit, or dodgy kill switch.

Whadaya reckon, coil?

What colour is the coil? Red or grey?

 

[Mad Hatter]

What colour is the coil? Red or grey?

Dark Grey

 

[Mad Hatter]

It’s like this one

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[ChasF]

Cracked coil can cause rough running but not heard of it causing the engine to cut completely. I’ve also had a faulty ICU causing similar symptoms to a faulty coil and a faulty kill switch which can usually be identified by flicking it on and off a few times to see if it changes anything. My bike is still on the original bean can, I’d check the new one you’ve fitted if it’s the last part you changed.

 

[Mad Hatter]

Thanks Chas, good suggestion

 

[mikeyboy]

When you say new digital bean can,
What make/ supplier?

 

[Mad Hatter]

BMW OEM one Mike. The bike was running fine for months after I fitted it so I doubt it’s that. Received wisdom is that a cracked coil would make it run rough but not make it intermittently cut out, so now I’m thinking more likely kill switch or ignition switch?

 

[Gelandestrasse]

Probably not it, but always worth checking, that your plug leads are firmly pushed into the coil.

You don't mention when all these new bits went on/cleaned (my bike had a new OEM loom fitted when it came from the factory) or how many miles you have done since 'months ago', but a bit of rubbish floating around the carbs/flooding can cause rough running until it clears; all the evidence evaporates away. Have you smelt your boots recently? (the outside!!) Which one smells more of fuel than the other?

Hope this helps.

 

[Mad Hatter]

Problem solved, turns out it was the coil. I had a new one on the shelf ready to be fitted to the project bike so I swapped it over and the basic is now running fine again. Thanks for all the pointers gents

 

[Mad Hatter]

After a truly dismal winter, today was officially a good day in the world of Mad Hatter, the sun shone, the roads were dry and salt free, the bike was running so much better with the new coil fitted, and a full day was spent on the roads of the Dales and Moors, all is good in the world, for today at least

 

[2gses]

After a truly dismal winter, today was officially a good day in the world of Mad Hatter, the sun shone, the roads were dry and salt free, the bike was running so much better with the new coil fitted, and a full day was spent on the roads of the Dales and Moors, all is good in the world, for today at least

Long may it continue Ian, I could bob in for a brew on my way home from milnthorpe next Tuesday morning if you’re about?

 

[Mad Hatter]

Long may it continue Ian, I could bob in for a brew on my way home from milnthorpe next Tuesday morning if you’re about?

You’d be very welcome Chris but alas I’m working darn sarf Tuesday - Wednesday this week

Give me a shout if you fancy going for a ride out one weekend though

 

[SteveHop]

Problem solved, turns out it was the coil. I had a new one on the shelf ready to be fitted to the project bike so I swapped it over and the basic is now running fine again. Thanks for all the pointers gents

Just out of interest did you find the problem by testing the coil or just trying a new one ?

If you did test it , did it show up a resistance error in the primary or secondary circuit ?

Just interested as i think i might have a coil problem

Thanks Steve

 

[Mad Hatter]

Steve,

I didn’t test the coil, I just did a swapnostic job by replacing the old coil with a brand new one I had sat on the shelf for a project bike I’m building (see new year new project bike thread). After I replaced the coil all the problems have disappeared the the bike is running much more smoothly and with noticeably more power.

 

[SteveHop]

Steve,

I didn’t test the coil, I just did a swapnostic job by replacing the old coil with a brand new one I had sat on the shelf for a project bike I’m building (see new year new project bike thread). After I replaced the coil all the problems have disappeared the the bike is running much more smoothly and with noticeably more power.

Ok thanks for the info , mine seems to be a intermitant problem , not sure if its the coil or the control module. I have another coil so will swop that first and see if it makes any differance .

 

[ChasF]

Ok thanks for the info , mine seems to be a intermitant problem , not sure if its the coil or the control module. I have another coil so will swop that first and see if it makes any differance .

Intermittent ignition faults tend to get worse. I’ve had trouble with the ICU and the kill switch as well as the coil.

 

[SteveHop]

Intermittent ignition faults tend to get worse. I’ve had trouble with the ICU and the kill switch as well as the coil.

Yes in a way it would be easier if it just failed and you knew which part to replace.
Ive tested the coil primary and secondery resistance and it seems ok , but i know that you can have micro cracks in it which cause the problem if heated.
regarding the ignition control unit , not sure how to test it , just check out the heat paste.

 

[ChasF]

Yes in a way it would be easier if it just failed and you knew which part to replace.
Ive tested the coil primary and secondery resistance and it seems ok , but i know that you can have micro cracks in it which cause the problem if heated.
regarding the ignition control unit , not sure how to test it , just check out the heat paste.

The easiest way to test the ICU is to swap it out. I think Siebenrock or Gletter supply a tester although that might be for the bean can