Make sure the tickover when warm is at least 1200rpm.
Other than that, you could try draining the carbs, just an egg cupful each (borrow Fazersharp's), and see if you maybe have any water in the tank. There are drain screws underneath each carb.
Be fully aware, the carb screws are made from melted cheese, if you have an ill fitting screwdriver or are a bit heavy handed you WILL round them off or break them.
I think they were manufactured by a piss taking mouse.
Another cheap option is to buy a litre of 99% Isopropyl Alcohol and put a third of the bottle in a full tank of fuel, over 3 tanks, and it will bind with any water in the tank and safely burn it off as fuel without any fuss at all. I use it every winter anyway to keep the fuel system free of moisture to prevent carb icing, it doesn't change any running features of the bike at all, apart from in this positive way.