Thread: Any ATV gurus here?

From my experience buggered brushes or dodgy earth rarely make the starter run by itself, normally they just won't turn over at all. Some models do throw off the magnets but again that stops them from going at all , not running away by themselves.
They do also have a habit of buggering the starter switch in switchblock .
Brushes are a simple fix but doesn't sound like the issue going by description and if magnets self destructed then starter replacement required.
Still my bet is on something other than brushes if it is activating itself so I would still start with relay or solenoid. That said they do chew up starter brushes fairly quickly.
Should be the same starter on 500 and 520 . I think you'll find part number changed due to different supplier.