Just thought I'd share a money saving tip with you with regard to 500K2 Clock Back Covers. Mine where damaged and so I looked for replacement. They are the type of clocks that have the oddometer zero nob at the ack of the clock and the only ones available are from Germany at about £96 plus £18 postage.
However, there is replica sets (they are actually SS but advertised as chrome) available for CB750K4 - K6 at about £40 - ie -
https://www.ebay.co.uk/itm/Honda-CB-750-K-CB750-K4-K5-K6-Clock-Bottoms-Speedo-Tacho-Chrome-Cover-Case/302689446031?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 - these fit except there is no hole for the rear oddometer zero nob (I think the 750K3 also had this configuration?).
I have just got my clocks back from Peter (Kent400 - excellent job - thanks Peter) and drilled/filed the hole in the back of the SS speedo back (relicating the original cover) and they are now a perfect replica of the originals with a savings of about £74! The rev counter back fits straight on.
As they are SS, there is no rust issues on the edges of the slot I cut - just be careful when you drill the SS as its very thin and can twist if you go up in big jumps in drill sizes - I auto-centre popped (supported behind), pilot drilled, went up at 2mm sizes and finished off with a taper rotary burr for the larger hole/elongation (oval).
Hope that helps someone!