hi since owning the bike it has had a slight roughish idol varying around 500 rpm on and off . when troubleshooting a previous issue (now fixed )i found that no 3 cylinder doesn't get as hot ( spray test ) as the others at idol but as soon as the revs hit around 3k it pics up to the same as the others can anyone suggest the possible reasons for this after 3.5-4k revs the bike runs great

 

Hi, has it got a good spark on that cylinder, if yes suspect carbs, do a spark test first to find out.

 

hi thanks for the reply yes seems to have a strong blue spark looks like im going to have to do a carb clean when work allows. looks like some work has been done on the carbs in the past as the drain screw on 3 or the carbs face one way and only 1 the other (instead of 2 one way and 2 the other ) will have to see if i can find one to replace it in the future

 

Mate I have a similar problem now and sometimes one of the cylinders won't fire giving a funny twin/triple exhaust note. It means you have a very rich mixture and engine is flooding and somehow other cylinders are able to fire despite so much fuel but this one cannot,
I'd say check the fpr as well when you are at it.