How to Rebuild a Yamaha Raptor 66 ATV Starter

Yamaha's Raptor 660 sport ATVs use an electric starter motor to bring their engines to life. The starter motor itself is little more than an electromagnet, which relies on a spinning, shaft-like armature attached to a round circular commutator. A set of carbon brushes provides an electrical charge when the starter button is pressed, turning the commutator through magnetism. A gear attached to the end of the armature then turns the engine's starter clutch until internal combustion can provide sufficient power to operate the engine. A damaged starter motor can be rebuilt, but only after performing a battery of tests.

Things You'll Need

• Phillips screwdriver
• 12 mm socket
• Socket wrench
• 10 mm socket
• Micrometer
• Hacksaw blade
• Multimeter
• Outer and inner starter motor end cap O-rings
• Torque wrench

Instructions

Starter Motor Removal

1. Park the ATV on a level work area and set the parking brake. Remove the seat, using the release lever at the rear of the seat cushion. Disconnect the negative cable from the battery's negative terminal, indicated by a minus symbol, using a Phillips screwdriver.

2. Loosen the clamp attaching the muffler to the exhaust pipe, using a 12 mm socket and a socket wrench. Unscrew the mounting bolts along the top of the muffler, using a 12 mm socket. Pull the muffler off the exhaust pipe. Remove the exhaust pipe nuts, located on the right side of the engine cylinder, using a 12 mm socket. Pull the exhaust pipe away from the engine.

3. Remove the parking cable holder from the right side of the starter motor, using a 10 mm socket. Unscrew the terminal nut from the top of the starter motor, using a 10 mm socket. Lift the electrical lead off of the terminal post. Pull the starter motor and O-ring to the right and away from the engine.

Starter Motor Inspection and Assembly

1. Remove the drive gear circlip from the end of the starter motor output shaft, using external snap ring pliers. Pull the drive gear off the starter motor.

2. Remove the pair of bolts from the outer end cap of the starter motor housing, using a 10 mm socket. Pull the inner cap and O-ring, located near the starter motor shaft, off the starter motor housing. Pull the series of washers off the end of the starter armature coil, the long, shaft-like structure at the center of the housing. In total, there will be a washer with four upturned tabs and three flat washers.

3. Pull the outer end cap off the starter motor housing. Slip all three shims off the end of the starter armature coil. Pull the brush plate out from the housing, then pull out the armature coil. Push the starter motor terminal post into the starter housing, then pull out the terminal and the attached brushes. Pull the armature coil yoke from the outer side of the starter housing.

4. Measure the diameter of the commutator, the wider outside portion of the armature coil, using a micrometer. The commutator should have a minimum diameter of 1.06 inches. Replace the armature coil if the commutator diameter is less than 1.06-inches.

5. Measure the undercut, or depth, of the grooves cut along the length of the armature coil, between the commutator and the output shaft. The grooves should be 0.03-inch deep. Cut into any grooves that are less than 0.03-inch deep, using a hacksaw blade.

6. Set a multimeter to the RX10 resistance range, indicated by an omega symbol, using the meter's selector knob. Touch both of the meter's probes to the commutator. The meter should give a resistance reading between 0.025 to 0.035 ohms. Move the meter's black probe to one of the grooves cut into length of the armature coil. The meter should provide a resistance reading of 106 ohms. Replace the armature coil if either resistance reading was not within its specified range.

7. Measure the thickness of the brush pads at both ends of the brush assembly. The brushes must have a minimum thickness of 0.20-inch. Replace the brush assembly, if either brush is thinner than 0.20-inch.

8. Push the armature coil yoke into the outer end of the starter motor housing. Place the brush assembly into the starter motor housing, followed by the threaded terminal post. Push the brush plate into the outer end of the starter housing, followed by the armature coil.

9. Slide all three shims onto the protrusion at the tip of commutator, then push the outer end cap and a new O-ring onto the starter motor housing. Place three flat washer over the armature coil output shaft, followed by the tabbed washer, facing its upturned tabs toward the tip of the output shaft. Push the inner end cap and a new O-ring over the output shaft tip, followed by the drive gear. Place a new circlip into the channel cut into the tip of the output shaft.

10. Push the starter motor bolts into the outer end cap, through the stater motor housing, to the inner end cap. Tighten the bolts to 3.6 foot-pounds, using a torque wrench.

Starter Motor Installation.

1. Hold the starter motor to the right of the engine. Push the starter motor drive gear into the engine crankcase.

2. Place the parking brake cable holder against the L-shaped tabs cast into the outer starter motor end cap, then screw the holder mounting bolts into place. Tighten both bolts to 7.2 foot-pounds. Place the starter motor lead onto the starter motor terminal post, then tighten the terminal nut into place.

3. Mount the exhaust pipe onto the engine. Loosely tighten the exhaust pipe nuts. Push the muffler onto the exhaust pipe, then loosely screw the muffler mounting bolts into place. Reposition the exhaust pipe and muffler until everything is aligned, then tighten the muffler bolts to 19 foot-pounds. Tighten the muffler clamp to 14 foot-pounds, Tighten the exhaust pipe nuts to 7.2 foot-pounds.

4. Connect the negative cable to the battery's negative terminal, then tighten the terminal bolt. Reinstall the seat onto the ATV.

References

• Yamaha YFM660RN Service Manual; Yamaha Motor Corporation