Hi all,

Experiencing stuttering under load when bike is warm (again). Last time it did this it burnt out the main wiring loom and a replacment loom (second hand) and Voltage regulator (new part) sorted it out. Now 3000 miles on it is doing it again.

Hoping someone may be able to help me understand the resistance readings from my coils.

Coil 1 = 14.51 K Ohms / 1.4 ohms

Coil 2 = 14.36K Ohms / 1.4 ohms

I understand the resistance on 2 valves should be 12.6 KOhms / 2.6 Ohms. I an not sure if resistance is different for the four valve and sure was these readings mean anyway? How likely would it be that both coils would be deterating at the same rate? Or could this indicate a dodgy reading from a not overly expensive multi meter?

I have no reason to believe these are not original coils and the bike has now done 77k miles.

Grateful for any advice. Every days a school day with a K.

Good evening, Gilly.

4V coil resistance should be, Primary: 0,5 ohm. Secondary: 13K ohm.

H Giles
I wouldn't be concerned about the difference from what Inge has quoted but one thing to do is to take a resistance reading from either plug lead terminal to the spade terminal where the brown wire attaches. This will tell you if there is any leakage to earth and if there is then make very sure the brown wires are connected well. If there is leakage and the brown earth wire is not connected or high resistance (not connected well) then you can get very low amperage but high voltage spikes introduced into the 12v system which in turn can fry some of those delicate solid state electronic components such as the regulator. I have seen this happen but not on a K bike.

Rick G wrote:H Giles
I wouldn't be concerned about the difference from what Inge has quoted but one thing to do is to take a resistance reading from either plug lead terminal to the spade terminal where the brown wire attaches. This will tell you if there is any leakage to earth and if there is then make very sure the brown wires are connected well. If there is leakage and the brown earth wire is not connected or high resistance (not connected well) then you can get very low amperage but high voltage spikes introduced into the 12v system which in turn can fry some of those delicate solid state electronic components such as the regulator. I have seen this happen but not on a K bike.

Thanks for the advice Rick. You will have to speak slowly as I am a bear of little brains. What should the reading be between the primary and secondary coil connectors or actually should there be no reading as they should not be in contact with each other?

Thanks Inge as always.

giles ...there should be no resistance .....at all ....that is infinity .....between the primarys and the secondary of the coils .....or any of the posts or terminals to earth terminals ...(with the wires all removed)



what hapens on our bikes is that the output (secondarys are double ended and have a plug at each end ) the voltage change - spike is induced from the primary to the secondary side via the ironcore (in the guts of the coils )

but i have seen rather nasty corrosion around the output posts ....obviously affecting quality and quantity of spark ....the real worry ....as rick suggests ...is when the coils have over heated (due to poor ignition leads , plugs etc ) and a break though of the insulation of the epoxy has started .....vey quickly the miniscule crack can absorbe moisture and then become conductive ...often between the primary and secondary sides of the coil assembly ....more likely in wet climates .... i recon that the iron core is part of the issue .....as it absorbs moisture , corrodes , expands and cracks the epoxy causing some electrical leakage ...= big voltage spikes and stuff where they shoudnt be .

the repocussions are sincinct ...a dead icu will soon come to pass ....

dont blame the harness for the issue ...but certainly maybe damaged as a result

lets hope you find the issue quick .

hope this helps ...

Thanks for the advice. You guys really are a font of knowledge.

Well one thing I can confirm is that I definately live in a wet climate. Going to hit a potentially small problem with a big stick as I need the K road worthy as I use it daily.

Have a new set of HT leads on the way (£35 from RealmEngineering for the set). Cap 1 fit was always a little suspect. Have asecond hand coils and another voltage regualator on the way. Fortuntaley Motorworks give full refund on second hand parts if they do not solve the problem. Hopefully can sort it out quickly.

On another note I noticed a few weeks ago one of the plugs was missing its nipple. The K has done at least 4k miles on this as it is not something I considered checking when I bought the bike. What could the possible effects of this be?

Thanks again.....never know before to long I may be able to offer some advice rather than just except it.

oh ! for a mere 1/8 of an inch...not much ....but the disadvantage of regular plug missfires ...and inconsistent power ....surely you noticed it ...every now and again ?....

but dont forget that every opportunity that 10-20,000 volts has to escape the normal path, it will, without prejudice nor favour .

And other effect of a missing nipple is that you get spark erosion at the connector inside the cap, over time it could be rather much damaged...and a problem to restore a good connection.