Topic: "Clunking" noise coming from Chain

[Captain07]

Hi There!

This is my first post, so apologies if this does not make it to the correct area.  Ive had my CB750k5 for about a year now.  Runs great with no issues and has 31,000 on the odometer.  However, In the last couple of months I've noticed a "clunking" noise coming from what sounds to be the front sprocket area.  It's not consistent, and can easily be replicated by putting the bike on the center stand and moving the wheel by hand in the direction of travel. 

There appears to be no "jumping" of the chain, and the chain appears to be in good condition/relatively new and properly adjusted.  I also cleaned and lubed it and closely inspected the chain for any irregularities.  I also removed the chain guard to ensure that was not hitting the chain, but no luck.

I don't notice it while driving as the engine noise seems to drown it out except while slowing down to stop, and I have not noticed anything different in how it handles.  It's enough to make me a bit nervous, however.

Any help is greatly appreciated!

[BenelliSEI]

Some pictures of th sprockets might help. Have you ever changed them?

[TwoTired]

The noise you describe sounds like classic irregular chain stretch/wear.

You say properly adjusted.  OK.   But, did you rotate the rear wheel to see if there are tight and loose spots in rotation?

Another thing to check is that each link pivots easily with no bind.

Yet another thing to check are of course the sprockets for wear.

Lastly, I once had an axle bearing that had crushed balls in it.  They would normally space them selves out keeping the axle centered in the hub.  But, under acceleration or deceleration they would gather together and allow the wheel to move forward on that side, slacking the chain during the event.

Cheers,

[BenelliSEI]

“Lastly, I once had an axle bearing that had crushed balls in it“

Ouch!

[TwoTired]

“Lastly, I once had an axle bearing that had crushed balls in it“

Ouch!

Got your attention, eh?
And some say men aren’t sensitive.  Phooey

[evinrude7]

The noise you describe sounds like classic irregular chain stretch/wear.

You say properly adjusted.  OK.   But, did you rotate the rear wheel to see if there are tight and loose spots in rotation?

Another thing to check is that each link pivots easily with no bind.

Yet another thing to check are of course the sprockets for wear.

Lastly, I once had an axle bearing that had crushed balls in it.  They would normally space them selves out keeping the axle centered in the hub.  But, under acceleration or deceleration they would gather together and allow the wheel to move forward on that side, slacking the chain during the event.

Cheers,

agree with TT's first two statements.  i had a chain that would clunk every time the one or two tight links would reach the front sprocket.  didn't know until i took the chain off to service it, that i had a couple of bad links.  could only hear it when sitting on the bike and rolling slow.  replaced the chain and it was gone.  not sure about the crushed balls comment. 

[strynboen]

is the senter stand rubbing the chain..?

[Jerry Rxman Griffin aka MuthaF'er]

Lift your chain up off the rear sprocket. If it clears the teeth get a new chain.

[Stev-o]

Hey Capt...welcome to the forum.  Sounds like you have a bad chain, I would pull it for close inspection.

Did you replace it with a CCC?! [chaepchinachain]

[Geoff Hastings]

I’d remove the casing that covers the front sprocket, then watch what happens as you rotate the wheel. If the chain jumps off the sprocket it can smash the cases and even jam the case into the gearbox locking the back wheel as had happened to the bike I bought.

[Captain07]

Some pictures of th sprockets might help. Have you ever changed them?

No, I have not changed them.  I've been learning as I go with this bike and troubleshooting things as they arise.  I attached a few photos of the front sprocket in different positions.

[Captain07]

Hey Capt...welcome to the forum.  Sounds like you have a bad chain, I would pull it for close inspection.

Did you replace it with a CCC?! [chaepchinachain]

Yeah I'm starting to think the next step should be to inspect it closer and perhaps replace it.  Its the chain I bought the bike with, so I'm not sure of what brand/quality of it.

[Captain07]

is the senter stand rubbing the chain..?

No, the bike has the original 4 into 4 exhaust on it.

[Captain07]

The noise you describe sounds like classic irregular chain stretch/wear.

You say properly adjusted.  OK.   But, did you rotate the rear wheel to see if there are tight and loose spots in rotation?

Another thing to check is that each link pivots easily with no bind.

Yet another thing to check are of course the sprockets for wear.

Lastly, I once had an axle bearing that had crushed balls in it.  They would normally space them selves out keeping the axle centered in the hub.  But, under acceleration or deceleration they would gather together and allow the wheel to move forward on that side, slacking the chain during the event.

Cheers,

Thanks for this, I agree in that I think I need to take a closer look at and/or replace the chain since I don't know the previous history of the bike.  I attached some photos of the sprockets in another post, and they don't look bad?  But then again I'm relatively new to this and could be way off base.

[RAFster122s]

Is the front sprocket tooth profile hooked? The angle makes it difficult to see clearly. If it is hooked you need to replace it, rear sprocket and the chain. Compare tooth profile of your sprocket to a new one...wear should be apparent.

[TwoTired]

Is that actual rust I see on the chain?  Are any of the pin pivots rusty as well?

Cheers,

[MauiK3]

Photo angle makes it difficult but the sprocket looks worn. When changing chain, sprockets that are worn should be changed.

[BenelliSEI]

That sprocket definitely is very worn and “hooked”. Based on the noise you’re hearing and what I see there, I’d suggest you replace both sprockets very soon. While the chain is off, make sure it is free and swivelling on every link. I’d soak it in a tub of old motor oil for a day (moving it regularly ) and them hang it up to drip dry over night. Give it a good wipe down and check every link is rotating freely. It looks too dry to me.

[Captain07]

Thanks everyone, This helps a lot.

My game plan is going to be to replace the sprockets and the chain in the coming weeks and see if that solves the issue.  Unfortunately I don't know the history of this bike or how it was cared for prior to owning it, so every new noise freaks me out a little bit!

I'm new to all of this (started as a Covid project and fell in love with it) so have been learning as I go with the help of manuals and forums like this!

[Stev-o]

My game plan is going to be to replace the sprockets and the chain in the coming weeks and see if that solves the issue. 

That sounds like a good plan.  And dont cheap out and buy the least expensive parts you see on ebay, good quality parts will last longer and be a better deal in the long run. Get some good lube too...

[Captain07]

My game plan is going to be to replace the sprockets and the chain in the coming weeks and see if that solves the issue. 

That sounds like a good plan.  And dont cheap out and buy the least expensive parts you see on ebay, good quality parts will last longer and be a better deal in the long run. Get some good lube too...

Thanks for that!  Do you have any recommendations, such as good brands to look for?  I did a quick search and found this kit from 4 into 1 that looks like what I need: https://4into1.com/chain-sprockets-kit-honda-cb750k-1970-1976/

[BenelliSEI]

Decent quality and a good price.

[Stev-o]

Decent quality and a good price.

+1.  Yes, D.I.D. and Sunstar are good quality parts.  Confirm how many teeth your existing sprockets have to confirm thats what you want and to keep current gearing ratio  [could have been changed at some point?]

[lash]

I’d remove the casing that covers the front sprocket, then watch what happens as you rotate the wheel. If the chain jumps off the sprocket it can smash the cases and even jam the case into the gearbox locking the back wheel as had happened to the bike I bought.

That case is cracked,you should look into that too..

[Captain07]

Thanks again everyone!  I finally got around to replacing the sprockets and chain, re-adjusted the chain, lubed etc and the "clunking" noise is gone and everything is working perfectly.

The front sprocket was definitely "shark toothed" and in rough shape compared to the replacement.

[Stev-o]

Thanks for the follow up. That should help fellow SOHC'rs in the future that have the same issue.