1985 Yamaha Tri-Z 250 / YTZ250N ATV Owner's Service Manual (P/N LIT-11626-04-40)

Yamaha owner's service manual LIT-11626-04-40 covers the 1985 Tri-Z 250, designated YTZ250N (model code 38W). It combines operating and maintenance information for the liquid-cooled two-stroke three-wheeler with engine and chassis repair procedures and electrical troubleshooting.

• Engine and transmission: Cylinder and piston inspection, crankcase separation, crankshaft removal and installation, clutch service, kick starter repair, and transmission inspection.

• Carburetor and intake: Mikuni VM32SS tuning, jet selection, float-height checks, reed-valve inspection, and illustrated intake components.

• Cooling system: Water-pump disassembly and inspection, radiator removal, cooling-system pressure checks, radiator-cap testing, and thermostatic-valve checks.

• Brakes and steering: Front and rear disc-brake pad replacement, caliper and master-cylinder service, brake bleeding, steering-head adjustment, and bearing inspection.

• Suspension and final drive: Front-fork rebuilding, Monocross shock settings, swingarm and linkage inspection, rear-axle checks, and drive-chain tensioning.

• Electrical diagnosis: YTZ250N wiring diagrams, C.D.I. ignition tests, lighting fault tracing, and coolant-warning pilot-light circuit checks.

This manual suits experienced owners and mechanics who are comfortable with precision measurements, electrical testing, and the special tools specified for internal engine work.

Engine Repair and Internal Inspection

Maintenance interval and lubrication charts accompany component torque tables, fluid-capacity specifications, and inspection limits.

Top-end coverage includes cylinder-head inspection, cylinder wear measurements, piston inspection, ring checks, and reassembly. The piston-pin notes warn that hammering a stuck pin can damage the connecting rod, piston, and bearing.

The clutch section covers friction-plate wear, plate warpage, spring checks, pressure-plate alignment, and release-mechanism adjustment. Transmission inspection addresses shift forks, cam grooves, gear teeth, and engagement dogs, with illustrated shaft and fork arrangements.

Crankcase separation is documented alongside the specified YU-01135 separating tool; the clutch holding tool is YM-91042. Engine removal also covers the Y.E.I.S. chamber and the pivot shaft shared with the swingarm.

Crankshaft service scope: Removal, connecting-rod clearance checks, runout measurement, and installation are covered. The manual refers out-of-tolerance crankshaft repair to a Yamaha dealer.

Carburetor Tuning and Cooling-System Checks

The carburetor working-range chart links the main jet, needle circuit, slide cutaway, and pilot circuit to their operating ranges. It helps identify which circuit corresponds to a running problem before changing unrelated settings. Altitude and temperature charts, rich/lean symptoms, and a tuning-parts table support that discussion.

Cooling-system coverage includes an assembly drawing, leak checks, cap-valve testing, and a heated-water thermostat test.

The water-pump section links abnormal coolant changes or milky transmission oil with pump inspection. Its assembly notes identify seal-lip damage and displacement of the seal spring as risks during impeller-shaft installation.

Forks, Monocross Suspension, and Brakes

The front-fork section explains how oil level, air pressure, and optional springs affect suspension behavior. An exploded fork drawing supports disassembly, seal replacement, bushing inspection, and reassembly.

Instructions for the Monocross “De Carbon” rear shock cover spring preload, rebound and compression damping, spring replacement, and removal and installation.

Rear-shock service limit: The manual warns against disassembling the pressurized cylinder or nitrogen reservoir. Gas-release instructions are specifically for disposal by Yamaha dealers.

Steering-head service includes bearing and race inspection. Swingarm coverage adds shim placement, linkage-bearing checks, and rear-axle runout inspection. Brake sections provide caliper and master-cylinder assembly illustrations, disc inspection criteria, and bleeding procedures.

Ignition, Lighting, and Warning-Circuit Diagnosis

Separate ignition, lighting, and signal-system circuit diagrams highlight the relevant paths within the main wiring diagram. Fault-finding charts cover weak or absent spark, inoperative lamps, and a coolant-warning pilot light that fails its check.

The ignition tests distinguish the source coil, pickup coil, engine-stop switch, and ignition-coil windings. Ignition-advance and lighting-voltage graphs accompany the electrical specifications.

Cable-routing drawings show electrical leads, control cables, fuel hoses, and coolant hoses in their installed positions.

A Preview of Piston and Ring Inspection Data

For top-end inspection, the manual lists standard piston-to-cylinder clearance of 0.060–0.065 mm. The associated measurement drawings identify the piston measuring location and how clearance is determined.

Installed end gap for the top and second piston rings is 0.35–0.50 mm. The ring-inspection pages pair this specification with the illustrated bore check, alongside separate ring side-clearance and piston wear-limit data.

PDF Bookmarks and Wiring-Label Readability

Search and navigation: PDF text search is unavailable. Embedded bookmarks cover chapters and selected subsections; the Warranty Information entry has no usable destination. Small wiring-diagram labels and wire-color codes are legible when enlarged.

One printable English PDF with 137 pages, including the contents pages, indexes, section dividers, and one nearly blank section page.