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Discussion Starter · #1 ·
Hi everyone,

The starter on '73 CB450 has not been working. Makes a gravely, grinding noise when the ignition switch is hit. The starter motor seems fine and when I look at the sprocket & chain it appears the chain is very loose and likely skipping. Is it possible the chain just needs to be replaced? Below are pictures of the sprocket, chain and casing. Does the discolored area in the casing look like wear from the loose chain? Im also thinking to replace the sprocket while Im here although it does seem to look like others for sale online in terms of wear.

Thanks!
Kalin

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We see this a lot - yes, the chain is a bit loose and there seems to be a bit of wear on the sprocket, but those two are very seldom - if ever - the problem. You could actually try it with the cover off and I think you'll find that the sprocket on the crankshaft is slipping in the "sprag" style clutch attached to the back of the alternator rotor. It's a simple enough fix most of the time, once you pull the rotor you'll see the design of it and the 3 parts involved, possibly only 2 needed (usually #2, 3 and sometimes 12, 3 each). Remove the bolt in the crankshaft (normal thread, NOT left-hand) and if you don't have a puller you can use a rear axle from a CB350 if that's available. If the cast housing for the assembly is loose on the rotor or cracked, you'll need to remove it and inspect the screws and threads in the rotor. If you do have those 3 screws out, either use Loctite or stake the screws into the slots on the back as a retention method when you re-assemble.

Also, if you look closely at the end of the starter motor where it comes through the upper case, it appears the o-ring on the nose of the starter is torn and a piece is loose in the area

https://www.cmsnl.com/honda-cb450k5-1972-usa_model453/partslist/E++11.html#results
 

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Discussion Starter · #3 ·
Thanks for the reply, super clear explanation. The chain is not just a little loose- it actually hits the casing. Isnt that an issue regardless of the sprang clutch slippage?
 

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Ancient Dad that "O" ring is part of a circlip and is ok. The circlip is wire... image.jpg
HTH
Nigel.
 

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Discussion Starter · #5 ·
So just to wrap this up- the starter works!

I ended up replacing the rollers, springs and pins in the sprag clutch and also replacing the chain. The springs were clearly worn out (much shorter than the new ones) and seemed to have a hard time holding the rollers in place. It seemed impossible to tell a difference between the new and old chain but sure enough, when the new chain was on there was significantly less slack and it definitely does not hit the casing as the original did.

Thanks all for the input.
 
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