SOHC.co.uk Forums > CB750

Starter motor

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adrian58:
Hi, in the process of restoring a 1973 CB750. All going well up to now but once or twice the starter motor spins without engaging. I'm guessing it's the starter mechanism. I've seen repair kits available how difficult is it to do. Any help would be appreciated.

bluemouse1006:
Hi
I have the same prob if I keep using the starter alot any news will be good

Amos

steff750:
 ;)  this is a easy fix on the CB750 as the starter ring is behind the alternator ,so its only on the side of the engine not in the middle like the Kawasaki 750
 you need to remove the alternator cover first watch for the small starter gear it might fall out on removal and watch where the washer should be located , then remove the large bolt holding on the alternator to the crankshaft you should leave the bike in gear and lock the engine with summit in the gears to stop the engine rotating you will need pullers to get the alternator off the taper on the crankshaft ,it is torqued up to 70lbs per square inch so it might need a tap to free it ,you can then carefully lift off the starter ring as the rollers and the springs will pop out in your case they might fall out in bits? you do not need to remove the crosshead screws holding the cover of the three roller bearings springs and pins . put in the new set of roller bearings springs and pins ,replace starter ring onto rear of alternator while depressing the roller bearing in their grooves , if you have done this correct you will notice that the starter ring will only rotate one way and lockup the other way .that means everthing is working properly .put the alternator back on the crankshaft and torque it up replace gasket and cover job done  ::)

K2-K6:
As steff750 says above they are fairly easy to work on, and a good description of how to do it.

Just to pick up on what Amos has said "if I keep using the starter  alot" if the battery is running down on this type of starter clutch then the initial torque given through the starter motor can fail to get the sprag clutch to bite hard enough to turn the crank against engine compression. Make sure the battery is fully charged and then see if you get any failures first...if it still slips then you'd be more sure that it needs new parts to correct it.

Bryanj:
Only thing I would alter is use the correct puller that screwa into the rotor and pushes on the crank as a 3 legged puller tends to do damage, also it was common for those cross head screws to come loose or shear off and the big gear can get "flats" on it where it is inside the rollers----these faults were more common on the 500Twin but did ocasionaly occur on the 750

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