The problem points mentioned on the linked website:
"The GR 650 also has a few weaknesses:
As with many of the twins in the GSX and GS series, the operational electrical components with Lima and regulator/rectifier are a critical point. Due to contact corrosion occurring on the right handlebar switch for the parking light/driving light, the alternator (connection of the 3rd phase) is overloaded due to the high contact resistance, after which the controller/rectifier “says goodbye” and in the end the battery is also “in the field”.
The gear pairs of the 3rd gear often suffered from material breakouts, so-called pittings, due to a lack of surface quality. However, this was remedied during the model update at the end of the construction period. The last weak point was the membrane in the fuel tap. As she grew older, she became incontinent and unintentionally released fuel into the carburetors."