Startup Error - What does it mean?

Fallen Angel - Yes, tested with the multimeter and compared to all the available specs it looks fine (I had reg/rec problems with the 400, so have had practise there)

Flymo - Thanks, I've already done that twice, but to be honest for a low mileage bike (16k in V plate 4k of which I've done since Nov) the poor thing is a bit of a state, it has been dropped and dented at some point in its life and a half-hearted attempt at repair was made, ie broken bits were preplaced, but scuffed, dented and bent bits were left if they were still functional. It also looks like its spend a lot of its time sweating under a cover, the paintwork doesn't suggest its been left outside long term, but corroded, green connector blocks and the like suggest damp has been a problem, I'm avoiding re-wiring connector blocks it I can help it, the idea being only fix it if its broke, but as I'm having one problem after another it's starting to look like a new loom of a complete rewire would be easier.

The poor thing is finally getting the loving care it deserves, but its a slow process as I hit a new problem every time I fix one. I could give up, but its not in my nature and despite a very rocky start I'm finally starting to get on well with the bike despite the probelms I'm having with it.

Doof

[flymo]

I think you may have answered your original question though which is that dodgy wiring and connections is likely the cause of the rev counter behaving like it is.