I would second the advice of a hefty dose of redex, I play around a lot with dead engines that have stood far too long and many a carb issue has been resolved by first spraying carb cleaner into the carbs accessible bits, letting it stand a bit then starting the engine and running it effectively on the carb cleaner then running the engine with redex treated fuel for the next few tankfulls, it's worked on about 10 engines this year that had truly awful carbs that had decade old fuel left in them or worse water, doesn't work miracles, but does save a lot of time and effort. I used it a lot on my 500/4 which had a habit of dumping fuel from the overflow if the petrol tap was left on for any length of time, roughly every 6 months it would get silky and dup petrol, redex generally sorted it. I have also had some luck soaking carbs in cellulose thinners instead of petrol in the tank, even running the engine off the stuff, when there's a lot of varnish in the carbs internals. Depends how bad things are and how much aerosol carb cleaner I have sat around. Last time I bought cellulose thinner it was significantly cheaper than petrol and my lawnmower that was suffering from stale fuel clogging it up ( frenzy out of neighbours skip), ran fine on carb cleaner though it smelt funny.
