Yamaha YZ125/YZ250 1989–1991 Service Manual Set (P/N LIT-11626-06-76)

Yamaha split the 1989 information into complementary volumes: use the W and WRW disassembly books with the shared operation, inspection, adjustment and tuning volume. The YZ250B manual combines all seven subject areas in one book.

Coverage limits: YZ125W coverage is limited to operation, inspection, adjustment and tuning; its separate disassembly volume is not included. No YZ250A manual is included.

PDF Search, Bookmarks and Page Totals

Text search and diagram detail: Manual text is not searchable in these PDFs. The W, WRW and B repair volumes have chapter and section bookmarks; the operation/tuning volume has none. The W/WRW “Back to Index” shortcuts refer to an external index file. Small wiring color codes require zooming.

The ZIP contains four printable PDFs totaling 687 pages. This includes 65 cover and preliminary pages across the four publications. The example setting-record sheets in the operation/tuning and YZ250B volumes are also included in the total.

Engine Teardown, Chassis Service and Race Tuning

The following selected coverage highlights preview the workshop content. Further topics include silencer packing replacement and YZ250B handlebar-position adjustment.

• Engine repair: Engine removal, cylinder and piston work, power-valve inspection, YPVS governor assembly, crankcase separation, and crankshaft installation.

• Clutch and transmission: Clutch and primary-drive service, kick-axle and shift-shaft work, plus gear, shift-fork and shift-cam inspection and reassembly.

• Fuel and cooling: Carburetor and reed-valve service, cooling-system pressure checks, radiator removal, and water-pump impeller-shaft and oil-seal procedures.

• Brakes and chassis: Wheel-bearing replacement, caliper and master-cylinder service, brake bleeding, steering-head work, and swingarm and relay-arm inspection.

• Suspension: Front-fork disassembly and assembly, rear-shock spring service, preload and damping adjustments, and symptom-based suspension tuning.

• Electrical diagnosis: Spark-gap tests, connector and engine-stop-button checks, coil and CDI-magneto resistance measurements, fault-isolation charts, and wiring diagrams.

For owners performing their own maintenance, Yamaha specifies qualified mechanical skills and recommends dealer service for work requiring special tools or equipment.

Engine Inspection and Reassembly

The repair sections provide step-by-step procedures supported by numbered exploded views, job charts, removal points, lubrication callouts and tightening references. Exploded assemblies for the YPVS governor and crankcase/crankshaft show component relationships during deeper engine work.

Top-end inspection covers cylinder-head flatness, piston-pin and small-end bearing condition, and power-valve movement. The YZ250B book also includes a cylinder-letter and piston-color matching chart for replacement selection.

Further checks address clutch housing and plate wear, governor-groove condition, crankshaft alignment, and gear and shift-fork condition. Factory reference tables provide standard and component-specific torques, fluid and premix specifications, service limits, running clearances and setting-parts information.

Special tools: Crankcase work references the YU-01135 separator and YU-90050/YU-90062 crankshaft installer components. Rotor and clutch procedures identify the YU-01235 rotor holder, YM-01189 rotor puller and YM-91042 clutch holder. The YZ250B manual also lists international 90890-series equivalents.

Carburetion, Cooling and Track Setup

The water-pump sections cover impeller-shaft and oil-seal inspection. Their service notes connect abnormal coolant-level changes, discolored coolant or milky transmission oil with the need to examine the pump.

The tuning chapters relate carburetor circuits to throttle range, spark-plug readings, weather and course conditions. The carburetor working-range chart helps identify which metering circuit relates to a rich or lean running symptom; gearing tables and suspension guidance support track-specific setup.

The carburetor cautions explain how lean jetting can overheat and seize the engine, while an excessively hot spark-plug heat range can cause preignition damage.

Fork, Brake and Rear-Shock Service

Front-fork exploded assemblies accompany seal, bushing and damper-rod procedures, oil-level setting and installation checks. The W/WRW fork chapter warns that bottoming the inner tube during removal can damage the oil-lock piece.

Brake procedures cover internal caliper and master-cylinder components as well as bleeding. Steering and swingarm sections include bearing inspection and side-clearance adjustment.

Rear-shock scope: Coverage includes removal, spring service, external inspection and installation. Yamaha treats the nitrogen-charged cylinder and tank as sealed; internal damper overhaul procedures are not included.

Ignition Fault Finding and Wiring References

Cable-routing diagrams supplement the electrical sections. The WRW book adds its own circuit diagram and coil/CDI-magneto checks; the YZ250B manual provides an electrical-component layout and wiring diagram.

The ignition inspection charts help trace a no-spark fault through connections, the engine-stop button, ignition coil and magneto before CDI-unit replacement. Test equipment includes the YU-03112 pocket tester and, in the YZ250B book, the YM-34487/90890-06754 ignition checker.

The fuel system, hot cooling system, brake hydraulics, ignition high voltage and gas-charged suspension require the precautions printed in the manuals.

Piston-Fit Specifications: A Preview

The W and WRW disassembly volumes specify a standard piston-to-cylinder clearance of 0.060–0.065 mm. The YZ250B manual specifies 0.050–0.055 mm.

These separate fit specifications accompany the top-end inspection material. They help distinguish the applicable measurement criteria when assessing piston and cylinder condition across the different YZ250 versions.