Calling 5 Twins, need jetting help

Sounds like you're on the right track. Other terms for the needle jet are "emulsion tube" and "atomizer." The carbs would have come from Mikuni with N8 needle jets. Curious to know what size you found in there. Good that the float levers were unmolested. I'm sure the pic is meant to show the parts measured and the measurement taken, not the procedure you used, and that you didn't measure from the top of the flange instead of the gasket surface; we don't want to mislead the unknowing.
N8 (168) The needle itself is SF-21 Mike knew right away that set up was wrong. I have no clue, never had to change needle and needle jet.
 
+1 to that! When Michael retires he's going to leave a huge gap.

This thread has drummed a in a lesson for me: Don't generalize. The generic NJs in the VM carbs I'm used to working with on the XS650 have to be leaned out substantially to work at all well even on hopped up big bore motors, so I assumed that the N8s would be rich enough--and we know what happens when we do that. Stepping up NJs would have been the next suggestion after confirming fuel level, but Michael had the knowledge to prescribe needles and a range of jets without a bunch of rounds of cut-and-try.
 
Mikuni needle codes begin with a number, not a letter, so your needle is probably a 5F21. This first number in the code designates the length series in 10mm increments. A 5 series needle would be between 50 and 60mm long, a 6 series between 60 and 70mm etc. Normally, a longer (leaner) 6 series needle is used.
 
There is no support knowledge at Mikes XS
Nor at any of their "partners". They are strictly retail sales. When they sell you sub-standard goods and you call them down for it, they can be difficult to deal with.
I wrote Mikes and DCC off long ago.
 
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