I own a K7 myself and have battled with the thought of throwing an earlier set of carbs on just for the parts availability. after going through my carbs multiple multiple times I do not see the need to switch out unless I decide on a better set of carbs(ie aftermarket).
Everything has it's own little tweak, the older style seems to have more readily available parts and the only problem with my accelerator pump was the rust that accumulated after sitting unriden for a long period of time in which it did need replaced, but after that and a carb rebuild I have had no problems what so ever.
the worst of my carb woes was that the injector nozzles (the copper tubes at the entrance) were warped and somehow turned shooting gas down and away from the entrance to the ports which puddled gas in the exit of the carbs and created a LOT of backfiring. with a pair of pliers and a screwdriver and some "gentle" coercing I was able to get them pointed in the right direction. I still need some tuning work but have turned the bike from an OK machine into something that is a very reliable and capable commuter.
