Topic: A new noise! not from the engine?

[Jim Shea]

I have noticed a distinct clonk noise under decelleration to a slow speed and then accelerating. Is this clonk a normal noise that comes from the suspension compressing? or could it be from the chain? or elsewhere? I have a cb 750 F1 1976...
Jim.

[bryanj]

Nope not normal could be a whole host of things like loose headraces; loose chain; bad sprocket cush rubbers------

[Chris Liston]

I had the same type of noise on my 550.  I couldn't find what is was at all.  Then my cousin took the bike out and noticed it too.  My chaine was loose and ever once in a while would hit the center stand.  Adjusted chain tension and its never been back.

[Jim Shea]

I did think it might be the chain, but there is no sign of it hitting the stand. I will check tension.
How do you check the sprocket visually, without removing?
Also, what are cush rubbers?

[Chris Liston]

while the bike is sitting on 2 wheels you can check chain tension.  it should only have about 3/4" if up and down movent at the bottom of the chain.   To set the tension you put the bike on the center stand and adjust the tensioners.  take it off the stand and check the up down play again.  Thats how I did it. 

[Einyodeler]

A stretched chain will also make the same type of noise.

[Jim Shea]

I think it may well be that. The chain does seem to be a bit slack!!

[Jim Shea]

Whilst lubing the chain, I spun the rear wheel a couple of times and the clonk could be heard!!! So, I have adjusted the chain, I hope it goes away now!!

[bistromath]

Jim, rotate the wheel a little at a time and check the chain tension. If it changes, or if you see frozen/stuck links, your chain is shot and should be replaced along with the sprockets. Also, if your chain tension adjusters are nearing their limit (last 3 notches in frame) it might be time to consider replacing.

To check for a stretched chain, pick up a link on the rear sprocket and pull it away from the sprocket. If you can lift it so more than half the tooth is showing, it's time for a new chain (and sprockets).

[Jim Shea]

There is less than half of the tooth showing, so I assume it is OK? the thread of the chain tensioner has quite a bit left, what do you mean by 'last three notches"
Cheers,
Jim.

[SteveD CB500F]

The cush rubbers are inside the rear hub and damp out the fierce "stop/go" shocks when you acc/decellerate.

By last 3 notches, I think Bistro means the marks on the swingarm that allow you to "line up" the rear wheel.  Inverted commas coz you can only really check wheel alignment with a piece of string as described in various (long) posts on here.

[Jim Shea]

Thanks, I thought they might be in another inaccessible place!!! Hopefully, it's not them making the noise!
Where is the adjuster for chain tension?
Jim.