I have a '02 Rancher 350FE. I replaced the battery, starter, and solenoid recently. It started right up and I rode around for 15 minutes (starting and restarting). I parked it and came back a week later and now it's blowing the main fuse. I've checked all the connections from the the battery to the starter (everything I replaced). I have constant 12V at the entry side of the main fuse. I believe the problem is past the fuse box (towards the ignition). I disconnected all the connections in the front (key, lights, etc.) and it's still blowing the fuse. The fuse blows instantaly. I've read the posts about the regulator, but they seem to suggest that wouldn't blow the fuse right away...just drain the battery.
Any suggestions on what to look at next?

 

If you have connected the battery backwards, this fuse will blow, so check the battery terminals first, positive to solenoid.

A faulty regulator on the 350 usually blows the fuse right away. Disconnect the regulator, fit a new fuse, if it doesn't blow you know you have a faulty regulator. if you want to double check, connect it back up again and see if the fuse blows.