Hey Pete
to the Org.
On a 2001 if all 4 are out and the fuse is good,its probably the signal relay. It lives under the dash on the left side.As far as I can remem there is no way to test it,other than to see if it has power. Meaning you can't test it to see if it has failed. About the only way you can find out is to swap it with a good one. If you know somebody close by with an early model,try that. The orange wire with the green tracer is yer 12V switched power. Remove the flasher unit,test there for power with the ignition on. If you have power,you could check all the wiring to the sigs. Has the tail section plastic been off? Perhaps a wire got disconnected. On early Busa's like yer 2001 the flasher relay also contains the side stand relay,same housing,maybe the same ground,but I would doubt it. Perhaps one of the other members knows of a test for this component,I don't.
Rubb.