A good test would be to check the voltage at each end of the starter cable from the battery through the starter relay down to the starter.
Sounds like he's got a bad connection in that circuit.
Also check the voltage from the starter button that energizes the starter relay. With ignition on, if he got a jumper wire and jumps it straight to the relay, will it turn the engine over or will it have the same problem?
My stepping stone to what I'm riding now.
Suzuki GSX250 '82
Suzuki GSX-R600 '00
Vulcan VN1600 Classic '06
Fitted: tachometer, genuine windshield, K Drive hard bags, upgraded Meanstreak clutch spring with Judges washers, Cobra Speedster Longshots, Dobeck TFI controller, Chucksters air filter plate, Mustang seats with drivers backrest.
Up coming items: volt meter, oil and temp gauges.