The 1986-2006 Yamaha YZ80, YZ85, YZ125, YZ250 repair manual by Haynes, covers the following motocross bike models:

• Yamaha YZ80, 1986-2001
• Yamaha YZ80LW, 1993-2001
• Yamaha YZ85, 2002-2006
• Yamaha YZ85LW, 2002-2006
• Yamaha YZ125, 1986-2006
• Yamaha YZ250, 1986-2006

Note: this manual DOES NOT include WR models.
Book Excerpt: 1986-2006 Yamaha YZ80, YZ85, YZ125, YZ250 Motocross Bikes Repair Manual BRAKING PROBLEMS 46 | BRAKES ARE SPONGY OR WEAK, DON?T HOLD

1. Air in brake line (disc brakes). Caused by inattention to master cylinder fluid level or by leakage. Locate problem and bleed brake (Chapter 7).
2. Pad or disc worn (Chapters 1 and 7).
3. Brake fluid leak. See paragraph 1.
4. Contaminated disc brake pads. Caused by contamination with oil, grease, brake fluid, etc. Clean or replace pads. Clean disc thoroughly with brake cleaner.
5. Brake fluid deteriorated (disc brakes). Fluid is old or contaminated. Drain system, replenish with new fluid and bleed the system (see Chapter 7).
6. Master Cylinder internal parts worn or damaged, causing fluid to bypass (see Chapter 7).
7. Master cylinder bore scratched. From ingestion of foreign material or broken spring. Repair or replace master cylinder (see Chapter 7).
8. Disc warped. Replace disc (see Chapter 7).
9. Drum brake linings worn (Chapters 1 and 7).
10. Contaminated drum brake linings. Caused by contamination with oil, grease, etc. Clean or replace linings. Clean drum thoroughly with brake cleaner (Chapter 7).
11. Drum warped. Replace drum (Chapter 7).
12. Drum brake cable out of adjustment or stretched. Adjust or replace the cable (see Chapters 1 and 7).

STEERING, SUSPENSION AND FINAL DRIVE GENERAL INFORMATION The steering system on these models consists of a one-piece braced handlebar and a steering head attached to the front portion of the frame. The steering stem rides in upper ball bearings and lower tapered roller bearings (early YZ80 models) or tapered roller bearings (all other models). The front suspension uses one of three basic designs: damper rod, bottom cartridge, or top cartridge. The rear suspension consists of a single shock absorber with concentric coil spring, a swingarm and progressive rising rate suspension linkage. The suspension linkage causes the suspension to stiffen as its travel increases. This allows a softer ride over small bumps in the terrain, together with firmer suspension control over large irregularities.
HANDLEBARS | REMOVAL, INSPECTION AND INSTALLATION
(Refer to illustrations 2.3a and 2.3b)

1. The handlebars rest in brackets on top of the upper triple clamp. If the handlebars must be removed for access to other components, such as the steering head bearings, simply remove the bolts and take the handlebars off the bracket. It is not necessary to disconnect the throttle or clutch cables, brake hose or the kill switch wires, but it is a good idea to support the assembly with a piece of wire or rope, to avoid unnecessary strain on the cables.
2. If the handlebars are to be removed completely, refer to Chapter 2 for the clutch lever removal procedure, Chapter 4 for the throttle housing removal procedure, Chapter 5 for the kill switch removal procedure and Chapter 7 for the brake master cylinder removal procedure.
3. Remove the upper bracket bolts, lift off the brackets and remove the handlebars (see illustration). On 1989 through 1993 YZ125 and YZ250 models, the lower brackets can be removed from the triple clamp if necessary. To do this, remove the bracket nuts from below and lift the brackets out (see illustration).

Subject: 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Yamaha 2-Stroke Motocross YZ80, YZ85, YZ125, YZ250 service, maintenance, repair. ISBN-10: 1563926628 | ISBN-13: 9781563926624 | Haynes 2662