Side drafts

Killer6 said
And I hear that a lot, they constantly need fussing over, WHY? "I had to constantly tune the engine" is ridiculous

…and yet, we hear it a lot. From people who've been there and done that. Some of them just bit off more than they could chew and didn't know what they were getting into. Some of them tried to cheap out and use bad (worn out or Chinese) carburetors. Some of them had unrealistic expectations. But even if we ignore all those…we still hear, from people who know what the duck they're doing and saying, about the constant fiddlefutzing multiple carbs require, especially sidedrafts.

Multi-sidedraft-carb setups can work well, but it does require a great deal of fussing and fiddling and tuning and tweaking to get there, and a lesser but still notable amount to stay there.

other than linkage deficiencies needing re-sync'd too often what "goes out"?

Well, first you have to get "in" (all the way correctly dialled in, jetted, calibrated, adjusted) and that takes a lot more work than most people realise, and it can drag out long. You get the car running well, then it gets 10 degrees warmer out and you find a new batch of problems to fix, so you fix those, but then it gets another 15 degrees warmer out and you've got new driveability issues and you're still having fuel-consumption issues, so you work those out, but now the damn thing is a bіtch to get started and keep running until it's warmed up, then the weather changes again, etc. I think a lot of the constant tuning need we hear about isn't trying to keep it tuned, it's trying to get it tuned. (And then yeah, there are linkage issues, too.)

Then you've gotta figure that most of the kinds of carbs you might conceivably use in a multi-sidedraft setup—SUs, Webers, Dell'ortos, Zeniths—are entire fields of study all their own, with a whole lot of stuff to know and a few "rock star" specialists who can make 'em walk and talk and devoted fans who can keep 'em working well, and then a whole bunch of people who know just enough to get in trouble and as a result think the carbs are junk.

All that said, there are multi-sidedraft setups that run well. Factory ones (Volvo twin SU or Zenith, Datsun Z-cars with Hitachi carbs, etc) that reliably work great—have cubic mountains of factory R&D effort and expense behind them. There have been some thoughtful, skilled aftermarket multi-sidedraft setups that run well—but they need a lot of planning, work, and dialling-in, and are never the result of just grabbin' parts and tossin' 'em on.

As for motorcycle carbs: Yep, been done. See Fopar's '63 Dart here and here.