I recently got my brothers old 2002 400ex running again after 3 years of not running, (this 400ex is bored to a 450). It was running good for the first 2 days, yesterday I tried climbing a very steep hill with it. I might of been revving the engine too much. The 400ex is stuck in a valley doesn’t move, and doesn’t shift into any gears Not even nuetral It starts up quickly though. I don’t think that any of the gears are stripped because I can’t understand why they would strip from something this powerful machine is supposed to easily do. Anyone have any ideas of what happened?