I was riding this weekend and while climbing a hill I stalled out well when I got turned around and started the bike back up it just reved and when i clicked down to first nothing. The shifter clicks and the drive gear even moves a little but the bike just acts like its stuck in neutral. I pulled the clutch out and the plates look good and theres plenty of pad left on the clutches. The bike is a 99 yzf400 if anyone knows what this could be please help. Oh also there was no noise or warning that something went wrong.