Starter drive assembly - 1973 Yamaha TX 750

Assuming the starter motor spins but doesn't engage to turn engine over to start you could have a bad starter drive which is part of the starter assembly or possibly damaged/missing teeth on flywheel ring gear. Depending on year and model vehicle, some starters you can replace just the starter drive otherwise you need to replace the whole starter. If you changed the starter look at the flywheel.

It could be a defective starter assembly. There are two parts to a starter assembly: the starter motor and the starter solenoid. The offending culprit is usually the starter solenoid. Test the starter. Mount the starter in a large vise. Using jumper cables, attach the ground cable from a battery to the starter body and a positive cable to the starter positive post, where the main battery cable attaches. Attach a jumper wire from the solenoid-activator connection. Carefully jumper this wire directly to the starter positive post. The starter should spin firmly, and the starter drive-gear forcefully extend. Examine the starter drive-gear teeth. They may show much less sign of wear than the ring-gear since they are much harder steel. Replace the starter assembly anyway. The problem is the solenoid an electromagnet--is weak and is not driving the gear far enough into the ring-gear. This improper mesh creates grinding with just enough force to start the vehicle. If you do need to replace your starter this site looks like it has cheap prices, free shipping and great reviews http://www.buyautoparts.com/starter.htm

the starter drive needs to be replaced in the starter also check the flywheel for damaged teeth before installing the starter.it maybe better to replace the starter assembly instead of just the drive.

Your starter drive us weak The drive or sometimes called "Bendix" is spring loaded and mounted in the nose of your starter. 2 options - pull starter, disassemble & install bendix or Just replace starter as an assembly (new starter comes w/new starter drive.)

Four types of starter motor are utilized depending upon the vehicle transaxle and assembly plant location. Manual transaxle equipped vehicles utilize a conventional starter motor which consists of a yoke, an armature assembly, an overrunning clutch assembly, a solenoid, a commutator end cover, a brush holder and a pinion drive lever. Automatic transaxle equipped vehicles utilize a reduction type starter motor which has, in addition to the components found on conventional starter motors, a reduction gear and shock absorber assembly.





Fig. 3: Starter motor assembly

1. Disconnect the negative battery cable.
2. Raise and support the vehicle safely.
3. Label and disconnect the starter solenoid electrical connector.
4. Remove the mounting bolts from the starter motor, then carefully lower the assembly from the vehicle.

To install:

1. Install the starter motor assembly complete with any shims that may be used between the engine block and the starter.
2. Install and tighten the starter mounting bolts to 17 ft. lbs.. (23 Nm).
3. Connect the starter solenoid electrical connector.
4. Lower the vehicle and connect the negative battery cable.

Hope helps.

Odds are that you have a broken spring in the bendix part of the starter drive,which is replaceable but at the same time is hard to find separate from the whole assembly.The whole assembly will run you about 55 to 90 dollars depending on where you find it.

Starter - REMOVAL & INSTALLATION
Starter removal on some models may necessitate the removal of the front support which runs from the corner of the frame to the front crossmember. If so, loosen the mounting bolt which attaches the support the frame first, then remove the crossmember bolt and swing the support out of the way.

The starters on some engines require the addition of shims to provide proper clearance between the starter pinion gear and the flywheel. These shims are available in 0.015 in. sizes from Chevrolet dealers. Flat washers can be used if shims are unavailable.

1. Disconnect the negative battery cable.
2. Raise and support the vehicle safely using jackstands.
   

If access to the wiring is difficult, the starter may be partially lowered before disconnecting it, but be careful not to stretch or damage the wiring.

1. Disconnect all wiring from the starter solenoid. Replace each nut as the connector is removed, as thread sizes differ from connector to connector. Note or tag the wiring positions for installation purposes.
2. If equipped, remove the front bracket from the starter. On engines with a solenoid heat shield, remove the front bracket upper bolt and detach the bracket from the starter.
3. Remove the starter mounting bolts. If a starter shim tab can be seen protruding out from between the mating surfaces of the starter and the block, remove the outer bolt first, then loosen the inner bolt. With the outer bolt removed and the inner loosened, most shims may be grasped and pulled from the top of the starter at this point. Once the bolts are removed, lower the starter front end first, and remove the unit from the car.

If no shim tab could be seen, yet shims or flat washers fall from the starter as it is withdrawn, stop and attempt to determine their locations. If possible, gather the shims for reuse during assembly. Shims without tabs must be positioned on the starter prior to installation, but the bolts may be held through the starter assembly in order to hold the shims in position.


To install:

1. If flat washers or shims without tabs were found on removal, position them on top of the starter using the mounting bolts to hold them in position.
2. Position the starter to the engine block and loosely install the mounting bolts. If tabbed shims were withdrawn during removal, position them before the outer mounting bolt is threaded.
3. Once the starter and shims are properly positioned, tighten the two mounting bolts to 25-35 ft. lbs. (34-47 Nm).
4. If equipped, install the front bracket and/or heat shield to the starter assembly.
5. Attach the starter wiring to the solenoid, as noted during removal.
6. Remove the jackstands and carefully lower the vehicle.
7. Connect the negative battery cable.

STARTER OVERHAUL
Drive Replacement

1. Disconnect the field coil straps from the solenoid.
   
2. Remove the through-bolts, and separate the commutator end frame, field frame assembly, drive housing, and armature assembly from each other.
   

On diesel starter, remove the insulator from the end frame. The armature on the diesel starter remains in the drive end frame. On diesel starters, remove the shift lever pivot bolt. ON the diesel 25 MT starter only, remove the center bearing screws and remove the drive gear housing from the armature shaft. The shift lever and plunger assembly will now fall away from the starter clutch.

1. Slide the two piece thrust collar off the end of the armature shaft.
2. Slide a suitably sized metal cylinder, such as a standard 1 / 2 in. pipe coupling, or an old pinion, onto the shaft so that the end of the coupling or pinion butts up against the edge of the pinion retainer.
3. Support the lower end of the armature securely on a soft surface, such as a wooden block, and tap the end of the coupling or pinion, driving the retainer towards the armature end of the snapring.
4. Remove the snapring from the groove in the armature shaft with a pair of pliers. Then, slide the retainer and starter drive from the shaft.

To assemble:

1. Lubricate the drive end of the armature shaft with silicone lubricant and then slide the starter drive onto the shaft with the pinion facing outward. Slide the retainer onto the shaft with the cupped surface facing outward.
2. Again support the armature on a soft surface, with the pinion at the upper end. Center the snapring on the top of the shaft (use a new snapring if the original was damaged during removal). Gently place a block of wood flat on top of the snapring so as not to move it from a centered position. Tap the wooden block with a hammer in order to force the snapring around the shaft. Then, slide the ring down into the snapring groove.
3. Lay the armature down flat on the surface you're working on. Slide the retainer close up on to the shaft and position it and the thrust collar next to the snapring. Using two pairs of pliers on opposite sides of the shaft, squeeze the thrust collar and the retainer together until the snapring is forced into the retainer.
4. Lube the drive housing bushing with a silicone lubricant. Then, install the armature and the clutch assembly into the drive housing, engaging the solenoid shift lever yoke with the clutch, and positioning the front of the armature shaft into the bushing.
   

On non-diesel starters the shift lever may be installed in the drive gear housing first. On the 25 MT diesel starter only, install the center bearing screws and the shift lever pivot bolt, and tighten securely.

1. Apply a sealing compound approved for this application onto the drive housing; then position the field frame around the armatures shaft and against the drive housing. Work slowly and carefully to prevent damaging the starter brushes.
2. Lubricate the bushing in the commutator end frame with a silicone lubricant, place the leather brake washer onto the armature shaft, and then slide the commutator end frame over the shaft and into position against the field frame. Line up the bolt holes, then install and tighten the through-bolts.
3. Reconnect the field coil straps to the MOTOR terminal of the solenoid.
   

If replacement of the starter drive fails to cure improper engagement of starter pinion to flywheel, there are probably defective parts in the solenoid and/or shift lever. The best procedure would probably be to take the assembly to a shop where a pinion clearance check can be made by energizing the solenoid on a test bench. If the pinion clearance is incorrect, disassemble the solenoid and shift lever, inspect, and replace worn parts.

Hope this help.

If the starter of your car crank slowly it means that there is a problem in the starter assembly.The owner of the car should work on the starter . the owner of the car should be able to locate and repair the starter .prepare the tools and equipment in repairing the starter .So that when the starter will function properly.First you have to remove the starter to the engine :disconnect the starter magnetic switch to the ignition switch and the battery.And dis-assemble the starter : first remove all electrical wires from the starter motor,remove the bolt from end head cover and cover band, remove frame assembly ,remove the solenoid remove the bendix drive pin,remove the pinnion housing, remove the lock ring,then remove the pinnion gear assembly.check if there are worn out or malfunctioning parts then repair or replace them.after repairing and replacing the worn out parts then assemble and install the starter back to the engine. If the owner of the car can't do the job done the owner of the car should go to a car shop mechanic , and let the car mechanic do the job.

Starter solenoid probably.
-----------------------------------------------------------------------------
Sequence of Operation

NOTE: An overrunning clutch in the drive assembly protects the starter motor (11002) from excessive speeds during the brief period before the driver releases the ignition switch (11572) from the START position (as the engine (6007) starts).

1. The ignition switch is turned to the START position.
   

1. The starter solenoid (11390) is energized, creating a magnetic field in the solenoid coil.
   

1. The iron plunger core is drawn into the solenoid coil.
   

1. A drive lever and pin (11067) connected to the drive assembly engages the starter drive (11350) to the flywheel ring gear.
   

1. When the iron plunger core is all the way into the coil, its contact disc closes the circuit between the battery (10655) and the starter motor terminals.
   

1. The current flows to the starter motor, and the starter drive cranks the flywheel (6375) and the crankshaft (6303).
   

1. As current flows to the starter motor, the pull-in coil is bypassed.
   

1. The hold-in coil keeps the starter drive engaged with the flywheel.
   

1. The starter drive remains engaged until the ignition switch is released from the START position.
   

#1 is the stater with the solenoid on top of it.