Actually I'm pretty sure the greasy fingerprints are mine.
Thanks to the help of Ghost0 I now see that I installed the large chain sprocket on the wrong side of the freewheel! My problem with the two chains making contact was a problem of my own creation.
Thanks for the great after sale service!
Every install is a little different. Just look at the variety of front engine mounts. Fitting and adjustment are all part of the process.