When I took the bike for its MOT I was speaking to the garage owner who originally imported the bike and sold it to my brother. He stated that he always changed the pilot jets on import bikes as he never knew how long they had been stood unused. Even though I had used the ultra sonic cleaner on the jets and thought they were clean, when I bought new jets the difference in the size of the main hole running through the jet was huge! The pilot jets I fitted were N424-21-35.
Once the carbs were re-cleaned of finest green and new pilot jets fitted the bike started up straight away and is running better than ever!