Does it act the same with the engine running at a little above idle speed? This will give you good voltage for the test.
On your XS2 the turn signal flasher has three prongs. ONe power in, one power out, the other ground. When you plug in the new flasher just be sure the new one plugs in where the brown and brown/white wires are. Ignore the third wire.
You flasher will be mounted under the tank or on the rear fender behind the battery.
Leo