I recently replaced a crank in a 2014 RMZ450 because the crank rod bearing went out. The guy that brought it to me said it was leaking oil from the vent tube the day it "locked up". The guy has rode the bike twice since I put the crank in. The first time everything was fine no oil coming from vent tube. The second time he rode it oil came out of the vent tube. He didn't change the oil in between rides. Question is why would it happen one time and not the next? Also what caused the rod bearing to go out so soon on a 450? Thanks in advance.