Dynamo nasty Whining noise

[Angus]

E3L Dynamo, Ok its not from one of my A’s but the same basic unit. After excellent service from Andrew at Priory Magnetos, it now has new brushes, oil seal (there is not one on an A10 version) and commutator end bearing. The drive end bearing appeared good and was unwilling to come out of its housing, so I did not replace it. It did not appear to be charging and so joined F & D and checked output, a good 12volts on the correct polarity. BUT when I connect F&D the dynamo (I think) makes a nasty whining noise. Disconnect and it stops. It makes it both before and after I connect the meter to check the voltage.
Should I keep running her as a daytime bike with it disconnected or is the expert opinion it just when on load and the new steel drive gear (again not A10 as this is my Norton).

[RDfella]

new steel drive gear

Is it possible on this machine to adjust the amount of mesh of the gears? Gears that are meshed too tight will whine (there are other faults that will do likewise, such as poor tooth form etc).
Reason I ask is because I'm finding gears I buy today seem to be marginally oversize, so the distance required  between centres ends up more than it should be.

[Angus]

HI RDfella, No adjustment on the Norton unlike the A's. Probably why Norton went fiber with the drive gear. It must be something like the mesh as it defiantly only does it when the dynamo is charging so under load. I have checked and the dynamo is turning so the clutch/spider thing is not releasing and so it is not that tight. Ill stick with the A's as ride anytime machines and use this as a day time bike. 

[Triton Thrasher]

They sometimes groan a bit when D&F are connected together.  But you don’t do that for more than a few seconds.

Is it noisy in normal service?

[Angus]

I TT
Yes when it cuts in to charge (left lights on for a while to force it) it whines the same as with F&D together.

[Triton Thrasher]

If your dynamo is spigotted into the casing, as on a Triumph, could the hole it fits into have got worn out of shape in the past, by chronically loose dynamos?

That might allow too-tight meshing. But why isn’t it noisy all the time?

[trevinoz]

You didn't change the drive end bearing and it may be whirring under load, the field coil does tend to drag the armature towards it.