I am working on a 2012 ATV 300. The rider was riding along and it just shut off. No electrical after that. He put in a new battery thinking it was low and he crossed the wires. Positive wires on negative post and negative wires on positive post. I corrected them but still no dash when you turn the key. What parts do I need to trouble shoot? I checked all the fuses and connections. Everything seems fine. In very new condition. The starter does engage and turn over when I jump the starter relay. Any ideas?

 

Did you check those fuses with a test lamp or meter? A visual inspection doesn't always show a blown fuse. Check that battery to fuse to ignition switch etc, circuit, and the earth leads. He may have blown the electronics anyway, but the engine would still turn over "on the button" if a fuse hadn't gone or a wire come loose.

 

Just looked at the fuses. They looked good. Replaced the ignition labelled fuses with new ones with no difference. I cannot locate the fuse that comes off the positive wire (usually glass one, if I am not mistaken). When I turn the key, nothing comes on. No dash lights.

 

It is normally that main fuse that blows as it is between the battery and regulator, this part of the circuit is before the ignition switch so can blow with ignition off.

 

What the others have said. Also, makes it a lot easier if you remove the seat and plastics off the bike so you can see the harness to trace wires, and possibly that hidden fuse. I remember this happening on one of my quads and the inline fuse was close to the battery off the red hot wire.