They suggest full fat come as a good carb cleaner, I guess you will then need a good after wash with petrol to clean the sugar away. Also say not to split the carbs ....
If it's been standing that long I would suspect fuel/carbs. Even a really thorough clean can leave tiny deposits of residue. Any chance you could get them ultrasonically cleaned? Any rubbers could be perished or split. You say it will run (I think) but starts spluttering. Is the petrol tank venting properly?
personally i would do a compression test and make sure the mechanical side of things are right then i would with the engine cold take out the plugs,make sure you turn off the kill switch and turn the engine over with the start button,fuel should slosh out of the spark plug holes after a bit,make sure the engine is cold as fuel + hot ex pipe = nee naww.if not then the carbs are not fueling the engine.if there is fuel then its prob over fueling.if the bike is running a fuel pump then this might be gammy,if you think this might be the cause then make a remote fuel tank from an old water bottle and some fuel pipe and connect it straight to the carbs.i would bet its the carbs or the fuel pump but its hard to pinpoint the prob from a 100 miles away.. best of look .mick.
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