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I remembered more about our carbs. Mikuni used different metal blends for different carbs. Aftermarket and performance carbs were cast from aluminum and didn't usually have porosity problems, some of the stock factory fit carbs were made from "pot" metal, usually "White" metal, which is a very porous metal, if not cast properly.
Then, there is the way the parts are cast, drop pour, suction, centrifugal spin cast, injection molded, all sorts of ways. Some ways have methods that remove air pockets (or, "voids"0, some rely simply on the weight of the molten metal pushing the air voids out of the casting.
I don't remember if the stock H series carbs were White Metal, or aluminum, some of them were very soft, and problem prone.
A case against White metal carbs and casting techniques: During a 40 year use, General Motors used carburetors cast and made from two major suppliers, Rochester Carb Division of G.M., and a stand alone company, Carter Carburetor.
Before Rochester came into being, G.M. used mostly Carter carbs, square bore 4 bbl's. There were two different designs, one was the earlier carbs, WCFB, then, a better design, the AFB.
WCFB was White Cast Four Barrel
AFB was Aluminum Four Barrel
Both worked well.
Then, Rochester came about, and a spread bore carb (smaller primaries, giant secondaries), Both called the "Quadra-Jet", or, "Q-Jet". They couldn't make enough of them for production, so G.M. contracted Carter to build a version of the Rochester Q-Jet to take up the slack. Both were cast in White Metal. The Rochester Q-Jets were good carbs, very little problems, no porosities. The Carter versions were dismal, porosities, bore plugs leaking, screw holes easily stripped out, a lesser mix of very soft White Metal, a lot less durable.
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FAQ
They 'leak' more with higher fuel level in the bowl, (as you'd expect) so I'm not sure where the fuel actually reaches, height wise, in normal running....