Poor idle and occasional cut out

Evening all, New to this site and this is my first post.
I have a K3 650s that has an M4 high level race system, BMC air filter and the fuel mapping has been modified (?so say?), all been on the bike for the last 3yr's. But in the last year or so I have had an issue with it's idling. I'll pull up at the front of a queue idling OK for a while then it dips to about 400rpm picks up and dips, doing this a few times and some times cuts out, and has cut out just as I was pulling away witch ant good nearly dropped it. It rides fine when on the move just an problem at idle. The only other time there was an issue was last summer in the rain, missfire, bogging down and cutting out got home cleaned it off and soaked in WD40 OK after that. I'm guessing an electrical prob just dreading doing the checks, and I need the bike for commuting now as my moped hack is dead. Any ideas welcome and thanks in advance.

[Spanner Man]

Good afternoon.


A dodgy connection on the Throttle position switch can give you all sorts of 'interesting' problems. Make sure the terminals are clean.


Cheers.

My bike suffers the same problem. A wipe of the spark plugs and a regap fixes the problem.

Obviously the problem could be also due to the mixture being a little lean at idle, but the spark plug fix solves it so I'm not going to fiddle about with it for now.