Look here for help first!
Apart from the illustrations, which (I think) are self-explanatory, I will add that I wholeheartedly agree that the cleaning of the gasket from the manifold mount is a real PITA; the easiest way to access it is after the removal of the carburetor. In lieu of a dedicated gasket scraper, I used a sharpened, non-flexible, "thick" putty knife, and then cleaned up the surface with a razor blade scraper.
The bulk of the hard carbon deposits were removed with ice picks, various screwdrivers and even various sizes of drill bits; this stuff is rock-hard, and my valve was totally blocked. The "tools" in the photos can only be used after 99% of the deposits are removed. The SIS casing and brake cable casing shown can be scrounged from a bicycle store; probably used material can be gotten for free, but if new material is wanted, it's only a few bucks.
I would also add that the second time I cleaned the valve, I used regular oven cleaner on the intake pipe and on the valve itself. No harm was done, and a lot more carbon was thereafter flushed. Note that this oven cleaner procedure was done after using the various scouring tools in the photos. I repeated the oven cleaner method a number of times, until the water flushing fluid came clear. Note also that this method may be harmful to the diaphragm if there is a leak in the valve's shaft; of course, if this is the case, the valve is probably shot anyway.
Tom M.
I went through with a good soaking of Deep Creep. I swabbed some gunk out with Q-Tips, then I went and ripped a front brake assy off of one of our trashed bikes. I frayed the ends and drilled the carbon out as best I could. Massive amounts of carbon came from the valve, let alone the big tube.