My K100 is throwing fits and 'loses' cylinders 2 & 3.  Spark on others very weak when checked. Will suddenly come back and all is well for a while till it happens again. Swapped coils around to see if it was a coil, but still 2 & 3. Fuel pressure checks out and pump working. At present almost no spark on 1 and 4, none on 2 & 3, so not running at all. Interesting dilemma that has me stumped - not very hard to do that though. Any suggestions appreciated. Thanks, Allan  

Does it run OK when cold and play up when hot which indicates the hall sensors are cactus. Also check the plug at the ICU just behind the steering head below the top tube is plugged in firmly.

Temp seems to make no difference. Will check plug. Thanks

don't check them ,,,, clean them regardless 
once your in there, best to get it done and dusted

good luck

Interestingly if i let the spark plug metal shrouds touch when testing for spark i get a magnificent spark. Does that point to plug leads ?

yes it does

the plug leads are resistive ...but the wire may have broken just at the crimp type socket termination (where the conductor is clamped to the electrode )

often the socket part that makes contact with the spark plug top corrodes up , this could be because they haven't been pushed home correctly , or the ferrule that fits on top of the thread of the plug hasn't been fitted when changing (especially the ngk types )

I would suggest get at least two elcheapo pre made ignition leads from your auto store (usually blue in colour , but ihave seen grey as well )  the resistive silicon type

and fit them to cylinders 1 and 4 .....or 2 and 3
then  tie some copper wire around the body (threaded section of the spark plug ) and make a connection to a screw nearby fit the leads to the plugs and coils  then turn the motor over (without any plugs fitted ) so it spins fast and without compression

observe the spark across the plugs  to see if it has made a big difference

hope that helps and you follow what I mean

cheers

Corrosion inside the plug cap will do that too. If it's a mass of green in there, introduce it to the nearest bin.

Used to have a 1971 Valiant Charger that would run fine and then just stumble for about 2-5 seconds at 90 MPH (no power at all) before running fine again ..went on for several weeks before i pulled the coil lead from the dizzy cap..inside of the coil lead holder (brass) was covered in green crap i assume was from water getting in and reacting with the brass over time ...far as i could work out the green stuff resulted in a high resistance that would result in no spark through the dizzy until the voltage rose enough to find another way to ground itself  to the nearest earth. Have seen much the same with spark plug wire connections. (and in those days Deoxit wasn't around)

Checked plugs and they had no ferrule on top. Found some and put them on which seemed to help but still inconsistent. Come to a halt now as went to go for a ride and fuel pouring down over motor. thought it was tank but no, the fuel line out of the tank had split. Replace that and still got fuel everywhere, so time to have a break. Can't see where it's coming from as it seems to be behind the air box above the injectors. Maybe another hose, but have to do a bit of checking. 

Seems the fuel leak is coming from the fuel pressure regulator. Have to put a post under fuel problems to see how to get to that. Manual doesn't help much. Thanks for your help with the spark. The i get the fuel leak fixed I'll let you know how it went !!

eeek ...could have  a lot to do with it not running also
hope you have a powder type fire extinguisher real handy

good luck

Found fuel leak ! Must not have had fuel return line clamped properly on fuel tank !! All good now and have taken chance to degrease engine behind air box too. All fuel lines now good and bike running smoothly, although the spark still seems very weak when i take plugs out and check. However since it's running well i'm leaving well alone. Thanks for your help.
Regards 
Allan