748 Dash Lights, Rev Counter, Etc Not Working?

I had exactly the same problem with my 998, brought about by hastily slamming down too many ill thought through wheelies.
I re-wired the entire light/instrument cluster, only to find I had dislodged something within the switch unit causing an issue with multi plug r/h side. If I recall, the current, not reaching its correct destination, sought the route of least resistance to earth which may have been via one of the front indicators (faint glow when lights switched on - no lights). Pull your multi plug apart and look for obvious signs of corrosion, clean and re-pack with the proprietary grease.
The speedo is a mechanical device however, so if you have been wheelying, you may need to replace the drive, as I did.

 

One of the two black relays that sit next to the battery, had the same problems on my 998 years ago. Cheap and quick fix.

 

Chris, you can get spurious and apparently unrelated electrical faults on the cluster with dirty or burnt contacts on the earth path, often intermittent rev counter, dash lights flickering with indicators and regular bulb failures which occur on different power circuits. The usual culprit is the earth pin in the main headstock to loom 19 pin (or 23 pin for later models) round connector below front rhs of the tank. It all earths through pin T on the older model (pins T and Z on later ones) and it is a regular issue not helped by the plug retaining water and the amount of stuff that earth path has to deal with. If you have a later model bike it is the same issue but there are two earth paths which help tie it down and make the circuits more reliable, pin T earths the clocks and pin Z earths the lights. Just open up the plug and have a close look for water, burnt or white corroded contacts, this plug needs a regular clean and the contacts treated with a contact preserver or silicon grease in any case.

Relays are
Yellow one 28740141A and the other 2 are 54140031A

 

I had the exact same issue around 6 months ago on my 748R. Spent ages looking over the bike and it turned out the round connector Denzil mentioned hadn't clicked in place. I disconnected the plug, cleaned the pins, twisted it back on and all was perfect again

 

Chris there are at least 3 main loom variations and three front loom variations for the 1.6 ecu bikes which include 19 pin and 23 pins round connectors for the front loom depending on the MY. The earlier bikes with 2 ph have different looms to the later ones and I think there is a variation for the three phase bikes between MY00 and from MY01 on. The front looms have similar variations and the injection looms for the P8 are different from the 1.6 fitted bikes. If the looms for sale are indeed new they should be marked with the part number which will make it easy to match. There are also variations between the bikes for example MY02 748R and 748/748S had slightly different looms. Finally there are variations in part numbers reflecting slight changes within the looms. If you buy new you would best order new with the correct part number for your MY.
However the core of most are very similar and there is not that much required between the various 1.6 bikes to make the looms work except if you are trying to match a 19 pins system with 23 pins one.
HTH