ABS
Hi Alkis,
What has previous owner done to check it? Has he/she had it to a dealer for testing? I've had mine pack up in similar circumstances a few times, though not in the last four years. I took it to the dealers (Allan Jefferies) and they plugged it in to the computer and re-set it. Costs about £25 like, but worth a try.
Mine still has 'funny turns' when it doesn't register when I start up. Apparently they can do this in a low voltage situation. Make sure everything else is switched off, and if you don't already, pull the clutch in when you fire it up. If mine doesn't register first time, it will usually do so after switching off and firing her up again. if it doesn't do it after three or four attempts, a ride of about hundred metres, switch of and fire up again works 99% of the time. If you haven't done so already, try these tricks, or get owner to. Then suggest a dealer check and re-set if possible. If that doesn't work, it sounds, as the previous poster said, potentially expensive...
Dave.