speedo showing 0mph!speed sensor knackered ?

[Dead Eye]

This happened to me as well...

First of all, check the lugs as darrsi mentioned. If they are intact then its a bit more of a pain as you likely need the new sender unit. I was quoted £100 for it, but my mechanic suggested looking for a second hand one. I ended up finding someone breaking a Fazer who still had the part which cost me £25 delivered instead - so certainly worth shopping if you can.

The 0k, 4k, actual revs thing is the diagnostics of the TPS telling you that something is wrong. It's described in the owners manual;