Yamaha YZ125, YZ250 1988-1993, WR250 1991-1993 Repair Manual

The 1988-1993 Yamaha YZ125, YZ250, WR250 repair manual by Clymer, covers motocross and off-road bikes, including:

• Yamaha YZ125, 1988-1993
• Yamaha YZ250, 1988-1993
• Yamaha YZ250WR, 1989-1990
• Yamaha WR250Z, 1991-1993

Book Excerpt: Yamaha YZ125, YZ250 1988-1993, WR250 1991-1993 Repair Manual ENGINE

CLEANLINESS Repairs go much faster and easier if your engine is clean before you begin work. This is especially important when servicing you engines top end. If the top end is being serviced while the engine is installed in the frame, note that dirt trapped underneath the fuel tank or upper frame tube can fall into cylinder or crankcase opening; remove the fuel tank and wrap the frame with a large, clean towel. There are special cleaners for washing the engine and related parts. Just spray or brush on the cleaning solution, let it stand , then rinse it away with a garden hose; see Chapter One.
SERVICING ENGINE IN FRAME Some of the components can be serviced while the engine is mounted in the frame (the bikes frame is a great holding fixture- especially for breaking loose stubborn bolts and nuts).

1. Cylinder head.
2. Power valve.
3. Cylinder.
4. Piston.
5. Carburetor.
6. Reed valve.
7. Flywheel rotor/stator plate.
8. Water pump.
9. Clutch.
10. External shift mechanism.
11. Primary drive gear.
12. Kick starter.

BRAKES

This section describes service procedures for the front and rear disc brakes. Brake specifications are listed in Tables 1-3 at the end of this chapter.
DISC BRAKE The front and rear disc brake is actuated by hydraulic fluid and controlled by a hand or foot lever on the master cylinder. As the brake pads wear, the brake fluid level drops in the reservoir and automatically adjusts for wear. When working on hydraulic brake systems, it is necessary that the work area and tools be absolutely clean. Any tiny particles of foreign matter and grit in the caliper assembly or master cylinder can damage the components. Consider the following when servicing the front disc brake.

1. Use only DOT 4 brake fluid from a sealed container.
2. Do not allow disc brake fluid to contact any plastic parts or painted surfaces as damage will result.
3. Always keep the master cylinder reservoir and spare cans of brake fluid closed to prevent dust or moisture from entering. This would result in brake fluid contamination and brake problems.
4. Use only disc brake fluid (DOT 4) to wash parts. Never clean any internal brake components with solvent or any other petroleum-base cleaners.

Subject: 1988, 1989, 1990,1991, 1992, 1993 Yamaha YZ125, YZ250, WR250 service, maintenance, repair. ISBN-10: 0892876182 | ISBN-13: 9780892876181 | Clymer M391