Just in the progress of fitting cables , I have been looking at diffrant pictures of M20s and routes of the cables but non seem to be the same.
Do the trottle and choke cables both go down the inside of the tank next to the upper frame . Likewise advance/retard cable , and best way to route the clutch cable .
I route the cables much as you've described, under the top frame tube, leaving things as loose as possible.
I pass the clutch cable over the horizontal bar of the bottom fork yoke & let it sweep down past the engine to the adjustment mount on the gearbox. No way this would be period correct I'm sure, but I find it gives the smoothest cable action.
