I had recently sucked up a bunch of muddy water and trashed the bottom end on my 08 WR450F. I am trying to understand the failure mode of how the mud got into the bottom end. Here is a picture of my airbox off the bike. The current connection is beside the airbox drain plug and goes into the "dirty" side of the airbox. I believe this is where I got the ingress of mud into the crankcase. Since I have AIS removed I am thinking of moving the crankcase vent line to that location since it is higher and is also downstream of the filter. Also, the airbox drain plug is just that, a plug. If any water or other junk gets into the airbox the only way out is through the motor. In the old days this plug was a one way valve and the water had a way to escape but I guess this is money saver for Yamaha just to shove a cap over the drain. Any thoughts on this?