It really seems to be more art and luck than any particular skill. The last several times I've worked on a stock carb I've ended up getting it right. I couldn't say how exactly, other than I must have some good Hitachi Karma built up. The 79 I sold worked 100% perfectly when I got done tuning it, the 77 my wife drives is fine other than it needs some tweaking to the linkage (won't adjust idle below 1k, but the secondary seems to open on the early side and give it some pep) and the 79 I have now was running perfect with the stock carb before I swapped on a Weber.
My 32/36 weber on the other hand has been a pain in the neck. The electric choke is either way over or way under choking, and the least little bit of crud gets into the strainer screen and its like I unplugged the fuel pump. Oh well, starts hard hot or cold but it runs like a racecar going down the highway.

It probably just needs a rebuild and some cleaning up though. My 32/32 Weber worked great, but I got tired of having to deal with the manual choke all the time.
I think getting a Hitachi to run right just requires patience, a carb that isn't worn out to start with (or new shaft bushings) and some luck. I struggled with mine for years, maybe now I've just got them broken in. Only real tip I can offer is that the mixture setting is about 3/4s of the problem usually. Get that dialed in and the rest usually won't keep it from running. That and I'd never have someone rebuild one for me after the horror stories I've read here. Rather do it myself with maybe a machine shop trip for doing the shaft bushings.