Redbeard you just beat me to it, I was going to ask the same question.
Just got my bike to start after meddling for 2 weeks. Finally took her out for a good run today and hey presto no revs being registered after about 50 miles.

I knew the tacho cable had come out of the block before I stopped the bike, but the inner cable was lost!
So, same question, does anyone have a spare inner tacho cable (I'll pay for it!), before I order from Z1 Enterprises at $12 a go (I'll just have to wait for it to arrive), ZPower want one of my kidneys for one!