Dragstar 125 starting probs.

When I push the start button the solenoid clicks but it takes a few pushes of the button to get the starter to move.

I had this problem before on a different bike and it turned out it was the main engine earth (black cable) to the engine. It was loose and corroded.

Could anyone tell me where the main earth cable is on the xvs 125 please.

Thanks!

(no rush, im not going to use it until the snow clears)