Datsun Roadster Forum-311s.org

Ah yes, the black art that is Emulsion Tubes! I've heard that even the "experts" don't completely understand (let alone agree!) with how they work. I spent a lot of time researching them for Dellorto carbs, and came across some pretty good discussion and literature about what does what (holes, steps, position of the step in the tube length, thickness of the step, hole size, hole position...). I found similar discussions for Weber as well. I think if you Google Emulsion tubes you'll eventually find stuff. I still have all my literature and books, but it's not Mikuni, and to be honest I don't recall seeing any. Dave would know! Still, I experimented with several in the SK Racing carbs I ran for a while (Weber internals) and the Dellortos and found significant changes in how the engine fueled. They have an influence on how and when the main system responds beyond what the air and fuel jets do (the jets set the mixture and the tube says "when" and under what circumstances, also highly influenced by float level which changes the fuels position on the tube and how the tube operates... at least that's what I recall). It would be fun to experiment with them anyway... won't hurt anything unless it's horribly lean and you're not paying attention! A wide band is a no brainer...

HAVE FUN! But I gotta say, this is why I'm EFI!

Kameari would make these for a reason, so its to help/overcome something, they are designed for racing from what I understand. That is all I know.

It’s a lengthy explanation, but emulsion tubes are designed to compensate for mid-throttle drivability issues. By changing the hole diameter, quality of holes and the vertical location you change mid-throttle responsiveness by changing the bleed rate which will richer or lean out the mixture. Unfortunately I don’t have time right now, but I will attempt to explain this later today hopefully.
Dave