C15 1965 primary chain and tensioner

[Tigerfeet]

In my previous thread about whirring in the primary drive (cured by increasing the amount of slack - thanks) I mentioned that I was left with a 'very slight noise on the overrun'.  This has now become a loud, very obvious, very unhappy noise.  I am still thinking that it might be the chain wearing in the brand new tensioner. But it might be something far worse...

From my reading of Rupert's engine book, which mentions retrofitting a tensioner to earlier C15 models - with no mention of needing to change the chain, it makes me think that I could temporarily remove my chain tensioner and run the bike without - as a test. If the noise persists, obviously it wasn't the tensioner - and hopefully its actual source will be clearer. 
As far as I can tell, there are only two chains listed for C15's: one for all of the standard models, and one for the trials models which have different primary sprockets.   

Can anyone confirm my thinking - roadgoing C15s all have the same primary chain and removing the tensioner just puts it back to how the earlier models were configured.

[rhyatt]

On the overun, the top length of the chain is the blackest.
Is it catching on anything ? That it does not catch on when pulling.

Has the chain simply bedded in and requires readjustment

[DAVE BRADY]

Hi,

A stupid design by BSA means that to check anything or make any adjustments in the primary involves removing the primary cover.
So with this off the chain should have 1/4" total up and down movement. Also check the chain alignment. Look for shiny sides on the clutch sprocket teeth where the chain is running out of line.

Dave.

[Tigerfeet]

Issue solved!  I took the primary drive cover off. Everything looked tickety boo. So I ran the bike - and the noise had changed and diminished - and was clearly not the tensioner or the chain. But perplexing. My pal came round, and we were hunting about. Then he sat back watching while I continued blipping the engine. And he idly observed that the C15 engine vibrated around in the frame quite a bit, unlike his Ariel....

So - we tightened the engine mounting bolts up really tight. And the strange noise has gone!

[rhyatt]

If all issues were that easily solved.

As an aside, I've just done 300 miles over 3 days on my c15 , over 100mpg