Thanks guys, I do visit here most days Bruce but haven't posted for a while - I promise to try to contribute more often!
I wish I could take credit for the flywheel Charlie but that was an EBay purchase, ex-washing machine if memory serves. I did spend a lot of time tidying it though.
Some photos here, since the video of the test run I have made and fitted a cylinder cover which I think looks better than the bare brass tube:
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Dave