[northwind]

Something bad to do with the fuel, I'd reckon, but I've not had that same fault- water in the fuel could be it, but IIRC is only usualyl a problem when you're right at the bottom of the tank- have you run the bike dry recently? have you had the tank up recently- could possibly be a kinked hose somewhere...

Did the problem vary at different points of revs? Ie did it clean up at high revs or was it across the board?Bad fuel/bits in the fuel could have gummed up your carbs...

I'd wait to get an opinion from someone who's had a similiar problem but I suspect the only way to be sure will be to strip the carbs and clean them with carb cleaner, plus check that everything's together and working in there.

I had one day's terrible running which sounded similiar to what you have, which I put down to a blockage in something fuel-related, as it passed on after one good high-speed blast. But I stalled at every set of lights and had to slip the clutch for ages at lower speeds all day...