I HAVE A 97 RF900 AND HAVE HAD THIS VERY SAME PROBLEM,YOU CAN BE RIDING ALONG AND TO START WITH JUST AS YOU THROTTLE ON IT FEELS AS IF IT IS RUNNING OUT OF FUEL,TO FIX REMOVE THE STARTER MOTOR,ALTERNATOR AND REMOVE THE STARTER GEAR CLUSTER COVER,YOU CAN THEN LIFT OUT THE CLUSTER GEAR ASSEMBLY AND IN THE MIDDLE OF THE SHAFT IS A SPLINED BUSH THAT IS PRESSED IN WHICH IS RUBBER INSULATED AND DRIVES THE ALTERNATOR .THE RUBBER BUSHING FAILĀ“S AND WILL SPIN IN THE SHAFT WITHOUT TURNING THE ALTERNATOR IT MAY TURN THE ALTERNATOR AT IDLE IF USING A VOLT METRE TO CHECK THE CHARGE RATE BUT WILL NOT SPIN AT HIGHER RPM THIS BUSH CAN BE REMOVED WITH A SCREW DRIVER OR SMALL CHISEL THIS PROBLEM HAS HAPPENED TO MY BIKE AT 18K AND AGAIN AT 36K NOW HAS 42K BUT HAVE NOT HAD THE PROBLEM SINCE and probs contact me by email