I had on and off this annoying problem of starter not spinning I figured the plunger or copper elements in the solenoid would be toast I ordered from the UK a repair kit consisting of new plunger new side copper connectors and various washers 10 days after ordering the stuff showed up on my door step one hour and it is back on and spinning every time , I had to remove the left jardine exhaust and pax footpeg all in all one hour 's work naturally bike is on a table lift which makes it easy.
so here is the step by step replacement in pictures
I do not know how you could ? but it is so much easier when the starter is on the bench.. the bolts on each side of the contact points were extremely hard to undo I needed to put the whole assembly in a vise , beside only two long bolts are holding the starter onto the engine case my starter BTW is not the OEM it is the upgraded denso starter used on the toyota something