1985 Yamaha TRI-Z Service and Repair Manual
The Tri-Z arrives for 1985 as model code YTZ250N, and Yamaha documented it under part number LIT-11626-04-40.
Coverage is the 1985 model year only, so nothing in the tables belongs to another season. Confirm YTZ250N on the frame before ordering, because the three-wheeler range shared little between years.
The manual takes you through inspection and adjustment schedules, engine disassembly, measurement and reassembly with service limits and torque figures, carburetion and ignition specifications, electrical testing, and chassis repair including steering, suspension, wheels and brakes. Wiring diagram and troubleshooting material are part of it.
Written for the dealer network rather than the buyer, the tone is procedural throughout. Use the book as the primary source for anything you would otherwise be estimating.