Yamaha WR250Z(K) 1997 Service Manual — Owner's Guide (P/N 5EN-28199-30)

This 532-page PDF reproduces Yamaha’s WR250Z(K) Owner’s Service Manual, P/N 5EN-28199-30, First Edition, July 1997. Factory model coverage is limited to WR250Z for Europe (5EN1) and WR250ZK for Canada and Australia (5EN3). The U.S./Canada references in the special-tool list identify alternate tool numbers, not a separate U.S.-market model. The volume contains English, French, German, and Italian. Its job-chart format is suited to mechanics and experienced owners who understand two-stroke service and have the measuring and special tools the procedures call for.

• Top-end and induction repair: Covers the PWM38 carburetor and reed valve, cylinder head, cylinder, piston, rings, and power valve, with removal, disassembly, carbon cleaning, inspection, adjustment, reassembly, and installation procedures.
• Bottom-end and drivetrain work: Details engine removal, clutch and primary drive, kick and shift shafts, YPVS governor, water pump, CDI magneto, crankcase splitting, crankshaft and bearing service, and five-speed transmission, shift-cam, and shift-fork repair.
• Chassis procedures: Includes wheel and bearing service, front and rear brake master-cylinder and caliper overhaul, brake-fluid replacement and bleeding, front-fork teardown, steering-head work, swingarm and linkage inspection, and rear-shock spring and bearing service.
• Ignition diagnosis: Provides a no-spark inspection chart, circuit-connection checks, engine-stop switch testing, ignition-coil and CDI-magneto resistance tests, spark-gap testing, and CDI-unit fault isolation.
• Competition maintenance and setup: Includes the race-cycle service schedule, spark-plug inspection and gap data, cooling and transmission-oil work, ignition-timing adjustment, carburetor jetting guidance, final-drive gearing choices, and fork, shock, tire, and chassis setup charts.
• Factory visual references: Contains the Cable Routing Diagram and Electrical Components and Wiring Diagram, plus exploded job-chart views for Crankcase and Crankshaft; Transmission, Shift Cam and Shift Fork; Front Fork; and Rear Shock Absorber.

Engine and Chassis Repair Scope

The specification chapter identifies the liquid-cooled 249 cc two-stroke single, PWM38 Keihin carburetor, YPVS, 30:1 premix specification for Yamalube 2-R or Castrol A747, wet multi-plate clutch, five-speed constant-mesh transmission, CDI magneto, and link-type Monocross rear suspension. Regional tables distinguish French compression and tire data, Canadian dimensional and steering-geometry data, and the Australian fuel requirement.

Engine reference data covers bore and stroke, piston-to-cylinder clearance, ring specifications, power-valve inspection, crankshaft alignment and runout, clutch wear, transmission gears and shafts, and component-specific tightening data. Assembly notes address piston-ring position, smooth power-valve movement, and staged crisscross tightening for the cylinder and head. The chassis tables add wheel, brake, fork, shock, steering, and swingarm specifications, along with lubricant, coolant, transmission-oil, and brake-fluid information.

Maintenance, Diagnosis, and Tuning

The publication treats the WR250Z(K) as a closed-course competition machine. Its maintenance schedule organizes top-end, YPVS, clutch, transmission, cooling-system, brake, suspension, linkage, steering, wheel, chain, and cable work around break-in and competition use.

Carburetor setup pages explain atmospheric effects, test-run and spark-plug evaluation, the relationship between throttle opening and each metering circuit, and selection of the main jet, pilot jet, air screw, needle clip, and jet needle. Chassis tuning covers optional sprocket and spring tables, fork oil-level and air-spring changes, compression and rebound damping, rear spring setup, and symptom-based suspension charts for different track sections.

The electrical chapter centers on the competition ignition and engine-stop circuit. It provides a dial-gauge ignition-timing check and stator adjustment—not a programmable ignition map.

Special Tools and Repair Cautions

The country-specific tool table lists both YM/YU and 90890-series numbers. Examples include the YU-01135-A/90890-01135 crankcase separator, YM-01189/90890-01189 flywheel puller, YM-01442/90890-01442 fork-seal driver, and YU-03112/90890-03112 pocket tester. A multi-piece crankshaft installation set, rotor holder, clutch holder, dial gauge, and ignition checker are also identified.

For major engine repair, Yamaha warns that the case halves must separate evenly and that the crankshaft must not be driven out or installed with a hammer, protecting the case mating surfaces and rotating assembly from damage. The rear shock is a firm scope limit: its separate reservoir contains high-pressure nitrogen, the cylinder and tank must not be opened, and scratches on the piston rod can cause oil leakage. Internal damper overhaul is not covered; brake and suspension repair should follow the specified bleeding, routing, torque, and final operational checks before the machine is ridden.