400/4 noisy transmission

[Josse]

I bought my 1976 400/4 about seven years ago as a scruffy Dunstall Cafe Racer non runner.  Recently I decided to get it running the  fault was with the wiring on the Lucas electronic ignition. I changed the oil and filter fitted a new battery and took it for fifteen mile run. The clutch is fine as is the gear selection the only thing that disappoints me is that in all gears there is a loud whine when the engine is under load or just cruising along. As soon as the throttle is closed and the bike is on the over run the whine completely disappears.
Any advice please I know I will have to strip the transmission to rectify the fault.  What parts are most likely to be worn?

Thanks
Josse   

[Trigger]

Welcome Josse,
You will not know for sure until you strip the bottom end. I would say that you will be looking at the bearings, Primary damper rubbers, primary chain and cam chain to be changed while you in.
You will not know what you will find until you strip it down.

[Lobo]

...fairly dumb question (but nice cheap answer)... the chain is not too tight?
And indeed welcome...
Simon

[K2-K6]

Welcome to the site Josse, as Simon suggests it's worth checking the chain tension to make sure it's not pulling really tight on the front sprocket bearing.

If it is internal gearbox bearings, then the whine comes from loosing the correct gap between corresponding gears as the bearings allow the shafts to move closer together or further apart. If that's the case you are better off not using it as this will trash the gears, you may be able to replace only the bearings otherwise.

Oh, i'll second Triggers advice also.

[Trigger]

Or you can do the Norniron option and get some ear plugs.

[Norniron]

YEP