Corrosion is a conversion process that changes one material into another. Rusting, converts iron to iron oxide. Iron can literaly rust away. So too, can the metal that the carb bodies are made of. They are an alloy of aluminum and other metals, one of which is zinc, I believe. Anyway, water is a catalyst for corrosion, of metals. The white deposits are usually accompanied by metal pitting, which is lost metal. If the water was not exactly PH factor 7.0, then there is also an acid/basic/reaction that can speed up the metal conversion process. I've seen brass inside these carbs get pitted from corrosion, too.
Do look for signs of metal conversion inside the carbs, and deal with as necessary.
Do scritinize the idle/slow/pilot circuits/passageways, and all exit holes. There are fourm and all of them must be able to flow fluid to any an all others.
The 750 PD carbs also have an accelerator pump, passageways to each carb, and a squirt nozzle in each to verify clear flow. The pump itself has two check valves that must be clear to flow in one direction and block flow in the other direction.
Do it all the first time, and you will reduce the number of times the carbs must come back off the bike.
Cheers,
