Starter motor

[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

[adrian58]

Thanks for all your advice. Just a few things as I'm a bit thick. Does the generator large generator cover have to come off or just the inner circular one. Can anyone suggest where best to get the puller and do I need any oil seals or gaskets. Have seen repair kits on Flea-bay for about £20 odd so it doesn't look too expensive a job. Thanks again for all your help.

[Bryanj]

You have to remove the complete generator cover, so a new gasket for that and to get wriggle room you need to disconnect the wiring under the sprocket cover but no gasket there

[adrian58]

Gee thanks Oddjob  that would be grate but I live near Cardiff so I'll have bit the bullett and get one myself. Just been out for a little ride round and showing off to my friends and  the starters been fine. Must have used it 20 or 30 times. Just wondering if maybe it was a bit stuck and freed itself. Maybe a forlorn hope but think I'll give it a week or so and see. Thanks again everyone for your all help I'm sure I'll be bugging you all again soon for more advice.

[Bryanj]

If you are in Cardiff, get all the bits then ride up to Gloucester to do the job and use my puller

[adrian58]

Well cheers for that. Gonna see how it works for the next week or so but that would be grate.

[Bryanj]

No problem, be advised i work permanent nights so email me with a pnone number to arange things and it will loose a small amount of oil