Here is some info on the 750 twin carbs, posted by Wiredgeorge
The Keyster carb kits work for the 1976-79 BS38. In 1980, Kaw changed the needle jet and jet needle as well as the pilot jet. Since the kits contain the jet needle and pilot jet, they will work fine for the 1980 BS38 if you reuse your old jet needles and use a #40 pilot jet type Mikuni BS30/96. In 1982, they started using BS34 carbs probably because the set is about 90 lbs lighter than the BS38s. Specs:
Type BS38 1976-1979
Main jet 125
Main Air Jet 1.0
Needle Jet Badge # Z-4 or Z-4
Jet Needle 4JN19-4 or 4HL12-3
Pilot Jet 45 or 40
Pilot Screw 11/2 + – 1/2t turns out
Starter Jet 110
Fuel level (from bore center) 31
