Yamaha MT-03 - Service manual > Starter clutch and A.C. Magneto

Removing the A.C. Magneto rotor

1. Remove:

• Torque limiter cover

CAUTION:

Do not remove the bearing "1".

2. Remove:

• A.C. magneto cover

NOTE:

Loosen each bolt 1/4 of a turn at a time, in stages and in a crisscross pattern. After all of the bolts are fully loosened, remove them.

3. Remove:

• A.C. magneto rotor nut "1"
• Washer

NOTE:

• While holding the A.C. magneto rotor "2" with the sheave holder "3", loosen the A.C. magneto rotor nut.
• Do not allow the sheave holder to touch the projection "a" on the A.C. magneto rotor.

Sheave holder 90890-01701

4. Remove:

• A.C. magneto rotor "1" (with the flywheel puller "2")
• Woodruff key

NOTE:

Use the rotor puller.

Flywheel puller 90890-01362

Checking the stator coil and crankshaft Position sensor

1. Check:

• Stator coil
• Crankshaft position sensor

Damage → Replace the crankshaft position sensor/stator assembly.

Checking the starter clutch

1. Check:

• Starter clutch rollers "1" Damage/wear → Replace.

2. Check:

• Starter clutch idle gear "1"
• Starter clutch gear "2" Burrs/chips/roughness/wear → Replace the defective part(s).

3. Check:

• Starter clutch gear's contacting surfaces "a" Damage/pitting/wear → Replace the starter clutch gear.

4. Check:

• Starter clutch operation

a. Install the starter clutch gear onto the starter clutch and hold the starter clutch.

b. When turning the starter clutch gear clock wise , it should turn freely, otherwise the starter clutch is faulty and must be replaced.

c. When turning the starter clutch gear counter clock wise , the starter clutch and the starter clutch gear should engage, otherwise the starter clutch is faulty and must be replaced.

Checking the torque limiter

1. Check:

• Torque limiter Damage/wear → Replace.

Installing the A.C. Magneto rotor

1. Install:

• Stator coil "1"

Stator coil bolts 10 Nm (1.0 m*kg, 7.2 ft*lb) LOCTITE

• Crankshaft position sensor

Crankshaft position sensor bolts 7 Nm (0.7 m*kg, 5.1 ft*lb) LOCTITE

NOTE:

Align the projection "a" on the stator coil with the slot "b" in the A.C. magneto cover.

2. Apply:

• Yamaha bond No. 1215 "1" (into the slits)

Yamaha bond No. 1215 90890-85505

3. Install:

• Starter clutch "1" (to A.C. magneto rotor)
• Starter clutch bolts

Starter clutch bolts 30 Nm (3.0 m*kg, 22 ft*lb) LOCTITE

4. Install:

• Woodruff key
• A.C. magneto rotor
• Washer
• A.C. magneto rotor nut

NOTE:

• Clean the tapered portion of the crankshaft and the A.C. magneto rotor hub.
• When installing the A.C. magneto rotor, make sure the woodruff key is properly seated in the keyway of the crankshaft.
•  Lubricate crankshaft end threads with engine oil.

5. Tighten:

• A.C. magneto rotor nut "1"

A.C. magneto rotor nut 80 Nm (8.0 m*kg, 58 ft*lb)

NOTE:

• While holding the A.C. magneto rotor "2" with the sheave holder "3", tighten the A.C. magneto rotor nut.
• Do not allow the sheave holder to touch the projection "a" on the A.C. magneto rotor.

Sheave holder 90890-01701

6. Install:

• Gasket
• A.C. magneto cover

A.C. magneto cover bolts 10 Nm (1.0 m*kg, 7.2 ft*lb) LOCTITE

NOTE:

Tighten the A.C. magneto cover bolts in stages, using a crisscross pattern.

7. Install:

• Neutral switch lead "1"

NOTE:

Route the neutral switch lead so that it is taut and route it under the speed sensor lead "2" as shown.

a. 5 mm or more

Electric starter

Checking the starter motor

1. Check:

• Commutator

Dirt → Clean with 600 grit sandpaper.

2. Measure:

• Commutator diameter "a"

Out of specification → Replace the starter motor.

Limit 27.0 mm (1.06 in)

3. Measure:

• Mica undercut "a"

Out of specification → Scrape the mica to the proper measurement with a hacksaw blade that has been grounded to fit the commutator.

Mica undercut (depth) 0.70 mm (0.028 in)

NOTE:

The mica of the commutator must be undercut to ensure proper operation of the commutator.

4. Measure:

• Armature assembly resistances (commutator and insulation) Out of specification → Replace the starter motor.

a. Measure the armature assembly resistances with the pocket tester.

Pocket tester 90890-03112

Armature coil Commutator resistance "1" 0.025-0.035 Ω at 20ºC (68ºF)

Insulation resistance "2" Above 1 M at 20ºC (68ºF)

b. If any resistance is out of specification, replace the starter motor.

5. Measure:

• Brush length "a"

Out of specification → Replace the brushes as a set.

Limit 5.00 mm (0.20 in)

6. Measure:

• Brush spring force

Out of specification → Replace the brush springs as a set.

Brush spring force 7.65-10.01 N (27.51-36.01 oz) (780-1,021 gf)

7. Check:

• Gear teeth.

  Damage/wear → Replace the gear.

8. Check:

• Bearing
•  Oil seal

Damage/wear →Replace the defective part(s).

Assembling the starter motor

1. Install:

• Brush seat "1"

NOTE:

Align the tab "a" on the brush seat with the slot "b" in the starter motor yoke.

2. Install:

• Lock washer

NOTE:

Align the tabs "a" on the lock washer with the groves in the front bracket.

3. Install:

• Rear bracket

NOTE:

Align the slot "a" in the rear bracket with the tab "b" on the brush seat.

4. Install

• Starter motor yoke "1"
•  Front bracket "2"
• Rear bracket "3"
•  O-rings "4"
•  Bolts

Starter motor bracket bolts 5 Nm (0.5 m*kg, 3.6 ft*lb)

NOTE:

Align the alignment marks "a" on the starter motor yoke with the alignment marks "b" on the front and rear brackets.

5. Install:

• Starter motor gear
• Circlip

See also: