Mikuni Super BN, circuit by throttle opening

5 rows across 5 columns, read from 1 named source, listed in full below. All 25 cells hold a recorded value. The figures are listed against 5 engine families, named below.

Only true under these conditions. This is a map of which circuit to reach for, not a set of values to copy. Mikuni does not publish jet sizes per watercraft anywhere in this manual, and the ranges above are the sizes that exist rather than the sizes you want. The idle figure the manual gives, approximately 1100 rpm, is offered as a rule of thumb and it tells you to use your own watercraft's owner manual for the correct idle speed instead. Everything here assumes the engine is otherwise sound: the manual is blunt that a mismatch of engine components or porting cannot be jetted around, and calls that a carburetion nightmare.

Adjust in this order	Circuit	Throttle range it controls	What it is for	Where it stops mattering
1	Low speed adjuster	Idle	Sets a smooth idle, working with the idle stop screw. Turn it in and out in small increments until the idle smooths out.	No effect past 1/3 throttle. Stated as an explicit exception to the overlapping-circuits rule.
2	Pop-off pressure	Just off idle to 1/4	Works with the low speed jet. Set by the needle valve and arm spring combination, and measured with a pop-off pump rather than looked up.	The regulator portion has no tuning effect past 1/4 throttle, although it goes on controlling the fuel supply above that.
3	Low speed jet	Just off idle to 1/3	The main fuel metering off idle. Sizes run 50 to 150 in increments of 2.5.	Overlaps the high speed jet from about 3/8 throttle, and changing it still affects wide open throttle delivery to some degree.
4	High speed jet	1/3 to 3/4	The primary tuning component from 1/2 to 3/4. Begins contributing at about 3/8, overlapping the low speed jet. Sizes run 50 to 200 in increments of 2.5.	Tested by holding a constant 1/2 throttle for a minute then opening fully: hesitation is lean, a second or two of clearing out is rich.
5	High speed adjuster	3/4 to wide open	The last circuit to set. Clockwise reduces fuel flow, counter-clockwise increases it, and maximum flow is at three turns out from closed.	Read on fresh plugs after holding wide open, or on a maximum rpm reading: lean or rich, it will not pull as high an rpm as when it is right.

Applies to: 650, 701, 750, 760, 800sxr

Where these figures came from

Mikuni Super BN Owner's Manual, pages 14 to 17, Mikuni American Corporation

5 rows · confidence high