starter clutch CB750F

[neat street]

Hi All
starting the engine is getting worse, push button, then horrible noise (sounds like starter clutch not engaging)? what parts would you suggest I should try and source to fix the problem? I think part No  28120300000 is the main item needed, but no stock anywhere that I can find (any ideas on where to get one). and is it an easy repair?
Thank you all in advance
John

[K2-K6]

Before you get any further with parts can you be certain that the battery has enough output?  the starter drives the crank through a sprag clutch which relies on a mechanical pinching effect to transmit the torque,  if the battery doesn't provide enough grunt this clutch can slip and make a screeching noise.

Try it with jump leads from a car connected to see if it's any better,  if not then you're most likely into repair.

[neat street]

thanks for your quick reply, the battery is new, and sometimes the starter will engage and turn normally then slip, other times (most) just slips (whining noise then clunky gear noise). I have seen clutch repair kits on fleebay, but not sure if I need to go deeper and get more parts (starter clutch itself?). If it is the starter clutch, anyone know where to get one from please? (DS and CMS no stock)

[K2-K6]

The clunky gear noise shouldn't really happen without something being strange,  I've never heard one do that. You may have to remove the alternator cover to make sure nothing is badly wrong.
They are generally reliable as a rule but doesn't mean they can't go wrong. Don't know how familiar you are with the components,  the clutch effectively comprises a large gear rotating directly on the crank with a series of pinch rollers within that joint,  as the starter spins the gear then the rollers are used to pinch directly on the crank surface and lock the two together so there is no clutch in effect but just the small components (rollers etc) so I guess that is what the repair kits are selling,.

Can you hear where the clunking is coming from? It's not from the starter solenoid is it?

[Bryanj]

If done early enough pins springs and rollers should cure it BUT i have seen the clutch assembly come loose on the rotor and/or break the screws, somewhere i have a NOS clutch outer. I have seen the big gear centre polished surface wear but not often

[neat street]

Hi Bryan and K2-K6
Thank you both for your help, I suppose it best to strip down and have a look, but wanted to try and order all possible parts first. I will investigate further and see what the main issue is. The clunking is def not from the solenoid, so will order the clutch repair kit first.
Thank you again, always appreciate you help and advise.
John

[Pertinax]

Hi all,
Just joined the forum, having found this site whilst searching for a cure to the starter clutch problems I am experiencing with my Honda 1982 CB750F.
I bought my bike as a non-runner, the last owner having tried to start it on a less than healthy battery and giving up.
So first thing I did was buy a new battery - genuine Honda item from John Oldfield in Southampton.
Fitted this and tried the button - just a click from the solenoid, so the next logical step was the starter motor, removed this and stripped it down to find it in very poor condition, including a completely rusted terminal post, so a quick search on ebay found a decent looking replacement for £50. fitted this last weekend (not an easy job!)
pressed the button and the starter motor worked fine, engine fired up but what an awful grinding noise! so next step was to remove the left-side casing to expose the main starter ring gear, idler gear etc. the first thing that did not look right was the fact that I could mover the starter ring gear from side to side, so, borrowed a puller from a friend and removed the complete clutch housing/starter ring gear off the crankshaft. From reading many of the postings on this and other sites it seems that loose bolts on the starter clutch housing are given as the main cause of the grinding/knocking noise but mine were very tight, so I don't think it is as simple as this.  Sliding the starter ring off the clutch housing revealed a very worn thin circular sleeve sitting on the shaft of the clutch housing, it seems that a previous owner had identified what I think is the cause of the knocking/grinding noise after start up, and reamed the starter ring out and fitted the sleeve to prevent any lateral movement of the starter ring. So, fitting a clutch kit, on it's own is not going to cure this noise, as a lot of postings have borne out, I suggest you check that the starter ring gear cannot be moved from side to side otherwise this is going to allow the clutch rollers to move about and cause the knocking. I have today taken the clutch housing and starter ring gear to my local engineering firm to have a new  bearing ring fitted, when I get this back I will re-assemble the starter clutch and post the results on here. Nick

[Johnwebley]

welcome to the forum.

 that is a massive first post,

 hope you get it sorted


 

[MrDavo]

Take it apart first, then buy parts.