Yamaha Tri-Moto, Tri-Z 250, YTZ250 1985 Factory Service Manual (P/N LIT-11626-04-40)

• Official OEM publication (P/N LIT-11626-04-40) for the 1985 Yamaha Tri-Z 250, YTZ250N (38W) racing three-wheeler
• 137 pages of factory specifications, clearances, tolerances, and mechanical data
• Includes 47 exploded-view diagrams, 8 torque-value charts, and 3 specific cooling system schematics
• Covers the Y.E.I.S. chamber, water pump overhaul, reed valve inspection, C.D.I. magneto testing, and cylinder head torqueing
• Details complete crankcase splitting, kick starter rebuilding, swingarm bearing replacement, drive chain tensioning, and Monocross suspension setup

Exact Factory Data for Your Workshop

Getting vintage two-strokes running right requires precise factory numbers. This digital PDF documentation gives you the exact engine, chassis, and suspension calibration data used for the original launch build of the Tri-Z 250 series. Having these baseline settings directly at your workbench provides a distinct workflow advantage, allowing you to cross-reference dimensions quickly to speed up any diagnostic process. The guide thoroughly documents the two-stroke engine top-end, transmission assembly, and clutch mechanism, alongside carburetor tuning guidelines tailored for varying altitude and temperature conditions. To save you an expensive trip to the dealership, the manual features complete step-by-step repair instructions for complex teardowns. You can confidently tackle procedures like splitting the crankcases, rebuilding the front forks, overhauling the water pump, and bleeding the brake fluid entirely in-house.

For chassis and handling, the reference details the front and rear disc brake systems, steering head maintenance, and Monocross "De Carbon" rear suspension setups. When servicing high-performance machines like the 38W-series, always prioritize shop safety, verify your equipment, and ensure your workspace is properly set up before testing critical components. When attempting a deep fix on these specific models, technicians should be aware of a few common pitfalls. The mechanical water pump seals are notoriously prone to failing and silently mixing coolant directly into the transmission, which turns the oil milky and accelerates bearing wear. Additionally, the Monocross rear shock contains highly pressurized nitrogen gas, meaning strict adherence to factory depressurization protocols is vital to prevent severe shop accidents. To support electrical troubleshooting, the manual provides comprehensive wiring diagrams, signal system verification parameters, and cooling system checks, including thermostat testing. Beyond the basics, the text is heavily supplemented with carburetor cutaway views, troubleshooting guide charts, maintenance interval charts, ignition timing graphs, and precise cable routing diagrams to ensure every part is correctly oriented.

Specifications and Tolerances

This manual delivers the exact measurements required for professional-grade component inspection. Engine performance parameters detail a standardized 246 cm³ displacement and an idle threshold of 1500 ± 50 rpm. You will find complete fluid capacities, documenting the 1.0-liter cooling system volume and 1000 cm³ of SAE 10W30 motor oil for the transmission.

Fastener specifications are strictly defined for safe assembly. Cylinder head bolt torque values are listed at 25 Nm (18 ft-lb) across the specific tightening sequence, while the steering stem nut torque is clearly specified at 85 Nm (61 ft-lb) within the front-end assembly data.