A 1999 ULTIMA with a carburettor is a G16-AT, code G16AT, and the factory book for it is LIT-19616-G1-60.
Yamaha kept the G16 in production long enough that one manual ended up spanning 1996 to 2002 and thirteen further variants, from the earliest G16-AP through the last G16-AX, plus every 36-volt car in the G16-EP to G16-EX sequence. Useful if the car in front of you turns out to be a later or earlier year than the seller claimed.
The reference is the one Yamaha wrote for its own service network. Expect the full maintenance schedule, engine and drivetrain overhaul steps in factory order, chassis and brake work with tightening torques, wiring diagrams drawn circuit by circuit, and troubleshooting tables that begin with what the car is actually doing wrong.
Fitment check: G16AT on the code plate.
