Is it the speedometer that doesn't work, or the tachometer, or both?
For the speedo, check that the speedo-cable is connected (front wheel hub to rear of speedo) - if it's there and secure, it may be broken internally.
The tacho is controlled electronically by the ecu. Make sure it is properly plugged into the harness, and that the wires are secure.
I'd suggest you purchase/download a service manual, but you may be better served by a competent mechanic who can see the bike in person.