It turned out to be the drive unit on the front wheel; the centre was missing and the inner composite wheel had broken.
All working correctly now.
It became very time consuming maintaining the old style web page, so I have built another, easier to update site and have attached this new blog so I can update it on a more frequent basis. The blog is about all the American bikes we do while the web page more about the single speed F-Heads. You can view it at http://www.f-head.com/