XVZ1300U is the 1988 Venture. Yamaha's reference for it is service manual LIT-11616-XV-14, the same book used for the 1986 through 1993 bikes and for the Venture Royale.
Working on a long-run model
Because one manual served eight seasons, the specification tables and procedures are written with the model codes attached. Confirming XVZ1300U tells you which figures to use where the years differ.
Chapters take the machine apart in order: general information, specifications and torques, periodic inspection and adjustment, the engine from removal through top end, clutch, transmission and crankcase, then the fuel and carburetion system, the chassis with its suspension and brakes, and the electrical systems with complete wiring diagrams and test values.
This is the book a Yamaha dealer would have had on the shelf when the bike was current. Order it by LIT-11616-XV-14.
