Yamaha Timberwolf YFM250, YFB250, YFB250FW ATV Repair Manual 1989-2000

The 1989-2000 Yamaha Timberwolf YFM250, YFB250, YFB250FW ATV repair manual by Clymer, covers the following models:

• Yamaha Timberwolf YFM250, 1989-1991
• Yamaha Timberwolf YFB250, 1992-1998
• Yamaha Timberwolf YFB250FW, 1994-2000

Book Excerpt: 1989-2000 Yamaha Timberwolf YFM250, YFB250, YFB250FW Repair Manual ENGINE TOP END

The engine is an air-cooled, single camshaft, 2-valve single. Valves are operated by a single chain-driven camshaft. This chapter provides complete service and overhaul procedures, including information for disassembly, removal, inspection, service and reassembly of the engine top end components. These include the camshaft, valves, cylinder head, piston, piston rings and cylinder block. The components located in the lower end of the engine are covered in Chapter Five. Before starting any work, refer to Chapter One and read the service hints and the detailed information relating to the use of the measuring equipment that must be used in this chapter. You will do a better job with this information fresh in your mind. Table 1 lists general engine specifications and Table 2 lists engine top end service specifications. Table 1-4 are at the end of the chapter.

ELECTRICAL SYSTEM

CHARGING SYSTEM The charging system consists of the battery, CDI magneto, fuse and a voltage regulator/rectifier. Refer to the following schematics relating to the charging system:

1. Figure 2: 1989-1991 2-wheel drive.
2. Figure 3: 1992-1993 2-wheel drive.
3. Figure 4: 1994-on 2-wheel drive.
4. Figure 5: 1994-on 4-wheel drive models.

Alternating current generated by the CDI magneto is rectified to direct current for storage in the battery. The voltage regulator maintains the voltage to the battery and additional electrical loads such as the lights and ignition systems at a constant voltage regardless of variations in engine speed and load.
CHARGING SYSTEM OUTPUT TEST If a charging system malfunction is suspected, make sure the battery is fully charged and in good condition before going any further. Clean and test the battery as described under Battery Testing in Chapter Three. Also make sure all electrical connectors within the charging system are tight and free of corrosion prior to making this test.

1. Remove the seat as described in Chapter Fourteen.
2. Check the main fuse. On 1989-1991 models, the fuse holder is on the right-hand side of the frame (Figure 6). On 1992-on models, the fuse holder (Figure 7) is under the seat, next to the battery. Open the fuse holder (Figure 8) and visually inspect the main fuse (Figure 9). If the fuse is good, reinstall it, and then proceed to the next step.

Subject: 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000 Yamaha Timberwolf YFM250, YFB250, YFB250FW service, maintenance, repair. ISBN-10: 0892878223 | ISBN-13: 9780892878222 | Clymer M489-2