Lumpy running...no acceleration, and a wet/black plug in cylinder one.
Culprits I suspect are:
Coil
HT lead
But could be also a fuel issue to cylinder one.
What's my troubleshooting sequence?
Thanks.

Hang on....wet/black plug means fuel IS getting through, so it's got to be electrical...?
So, I need to test the HT lead to no. 1 cylinder, and test the coil.
Presumably I'm taking resistance readings...I'll go and do the lead now, and I'll be back shortly. 

HT lead is kind of fluctuating..I have the metre set to 2000K, and I get an average of about 1700? Moves up and down though.
I have the coil in front of me now (once I cleaned it up!)...I'll mess about with it and keep an eye out for any pearls of wisdom.

I thought the coils were one coil for two cylinders. It could be an HT lead failure or it could be an injector not closing. Clean up the injectors or move one to another cylinder. If the problem moves with it then the injectors need replacement.

Good to know if it is a K75, 100 or 1100.

K75S 1988 Three cylinders, single coil serving each cylinder. I've been looking around but I can't find any good info on how you go about testing this type of coil and its lead. Different to the K100.

The easy way 1;
Get a multimeter and check in Ohms the coils. The bad one will present itself.

The easy way 2;
Switch "bad" coil to another cilinder. Ride the bike and check plugs afterwards.

The dirty way; Just get another coil and forget about this one.


Edit;
There is a good way to test the coils, some companies have special equipment for that.
Bad news, they're hard to find.

Although spark plug quality has improved they can still fail.
Regards Martin.

Turns out that an injector was the culprit. Pulled out the injector on the offending cylinder. Good clean up, and then gave it a few shots of brake cleaner. Re-installed, and popped in a bottle of injector cleaner. Seems to have done the trick, and seems to be smoother than before...but that could just be placebo!?!
An idiots guide to testing coils( both K100 and K75) would be a useful thing from someone who is well versed in electrickery....its my weakest knowledge area I guess.
Thanks for all the responses.

Run a couple of bottles of Techron through your tank, half a bottle per tankful. Bricks appreciated this treatment at least once a year.
Regards Martin.

BooG wrote:Turns out that an injector was the culprit. Pulled out the injector on the offending cylinder. Good clean up, and then gave it a few shots of brake cleaner. Re-installed, and popped in a bottle of injector cleaner. Seems to have done the trick, and seems to be smoother than before..

Good to know
Ride safe will ya?