[embee]

As all the above suggestions.


I had an odd problem end of last year, it was for all the world like a blocked idle jet which occurred suddenly (shortly after refuelling) Cut a long story short, after a lot of cleaning carbs etc it turned out to be a plug gone down, the refuelling was pure coincidence. New plugs and it ran perfectly, so in case you haven't changed them (even though they look OK) it's a cheap tryout.