Welcome smoothseven,
Sorry to hear about your friend.
Before doing anything to the bike or taking advice from other platforms always double check on here. You will get honest advice on the workings and their quirks and there is just about nothing on the XS/TX 650 now that hasn't be thoroughly examined.
Id the Vin no for help with making sure the correct parts are identified.............Carbs changed their jetting and there were some differences every 2 years and the jetting cant be mixed and matched between carbs.
Identify the charging system, (under the round plate on the left side of the motor that has Yamaha stamped on it), and one of the first things that needs to be done is to test the charging output, have a Battery that is in good condition, (holds a charge).