Rebuilt C15F whirring noise from the primary chaincase

[Tigerfeet]

My recently rebuilt C15F has a pronounced whirring noise from the primary chaincase. I've been in once to take a look and nothing looks out of order and there are no witness marks anywhere on the inside of the cases.

I'm now thinking about the chain tensioner. The tensioner was like new, with no grooves in it. My understanding (from Volume 1 : The Engine) is that the chain plates eat their way into the hard chrome face until eventually the rollers come into contact. I'm beginning to think that the noise I am hearing is this 'grinding/cutting' process taking place. And therefore I should ignore it.

Can anyone confirm that a certain amount of noise is generated by a new chain tensioner during the bedding it process?  (I'm finding it a little hard to imagine that back in 1966 folks rode away from the BSA dealers with their new bikes making this whirring noise...) 

[rhyatt]

When I treated my C15 to a chain tensioner , I found the adjustment slot was a fraction too short , thereby causing the chain to be way too tight.
From memory , 3/8" slack.
I opened the slot a whisker and was far happier with the tension it gave.
Do you have 3/8" slack?

[V500]

Have you checked the rotor/stator clearance?

[Tigerfeet]

The rotor stator clearance was very carefully set up. I don't believe that it could have moved. But will check.

The chain tension might be the issue. Rupert says 1/4" up and down play - and 'free to wobble up and down by 1/4"  which I take to mean 1/2" total movement. Haynes says 1/4" free play - which I take to mean 1/4" total movement. And the original BSA Instruction Manual says 1/8" of free play. Which I take to mean 1/8" total movement. I cannot rememember which book I was referencing when setting this up... so I'll get in there today and set it to the slackest of those three sources (assuming it isn't at that already).

[limeyrob]

Set it slack but make sure it can't hit anything.

[rhyatt]

I'm pretty sure it is total 1/4" free play.
1/8" down from centre and 1/8" up

Take care the alternator wires must face outwards from the stator and then they swing up and over the chain before entering the grommet

[Tigerfeet]

I went with the Rupert figure - and the whirring has gone. (Alternator cable is well clear.) There's still a very slight noise on the over-run, which I believe is when the bottom chain run is loaded, which means the chain tensioner will be getting most 'bedding in'. So I'm happy to accept that. Thanks all.