October's Classic Bike Guide (UK) has a number of great home-brewed machines. Most interesting for me was a hugely re-engineered Sunbeam S8, which appears also at:
http://www.onthebeam.co.uk/Specials.htmlThe owner has used his ultra-bike-shed skills to sort out all of the the machine's flaws (weak shaft drive, poor cyclinder head design, weak clutch etc.).
He actually machined a new cross-flow head from a billet of alloy, into which he arranged Kawasaki valve gear.
The obvious question that weighs down on you as you read the article is: if a guy can sort the ruddy thing out in his shed, why on earth could the BSA/Sunbeam empire not get it right with the resources at their disposal?
A sister machine to this a special is featured in the same write-up. This is a "Moto-Beam" - a Moto Guzzi V50 motor dropped into a Sunbeam chassis. And I tell you what, it fits like a glove.