Magdyno fibre drive gear - noisy?

[Greybeard]

Both my B31 and Ariel single suffer from what I think is excessive mechanical valve gear type noise (what do you mean, I shouldn't have old bikes then?  ) that I'm pretty sure is due to the backlash between the dynamo gear and the fibre gear. I've narrowed it down to that area - it's more distinct on the B31 than the Ariel - with the trusty stethoscope. Before I stump up the brass on ordering new gears, has anyone replaced them and noticed a distinct improvement?
I know that noises can be notoriously difficult to track down but pretty much everything else has been addressed now.

Steve