Hi, do all the other lights on the display still work? It'll do you no harm to check the fuses. It could be the speedo sensor but with revs not working it might be something else. Check and clean the multi plug in the back of the clocks, and check the speedo sensor is firmly in place. Back of the clocks and at front wheel centre, make sure the lugs are properly seated.Check the TPS for the revs. Turn ignition switch on, and unplug the TPS, it's the black plug on the right hand side of the carbs. It should go to 5000 if all's well.