Oil Tank Breather/Vent Hose

[BNasty]

I have a 2007 Yz 250F. This weeked at the track the breather/vent hose for the oil tank disconnected from the crankcase. I noticed it when I put the bike back on the stand and saw oil everwhere. There was still some oil in the bottom of the case. I got lucky in that the engine did not seize. The line is not a pressurized line, it is rubber and runs from the top of the oil tank to the bottom of the right side crankcase. The hose is connected using a fitting that appears simply to pop into the case.

I am very confused as to how this hose disconnected. I did not hit anything or anyone. I was riding on the track under normal conditions. There is the occasional rock on the track but I would not describe the track as rocky. The stock plastic water pump guard generally protects/covers the area where the hose connects to the case.

I had changed the oil prior to my ride, but this is not a hose that is removed to change the oil. I cleaned the fitting off, tapped it back in, filled the bike up with oil and tested the fitting. I am going to do a fresh oil change soon to see if there is any metal in the oil, but I just thought I would put the feelers out there to see if anyone has had this happen and/or is someone could offer an explanation as to how the hose disconnected.

[701yamaha]

Unlikely, maybe excess crankcase pressure popped it out???? How is your crankcase vent?

[BNasty]

Excess pressure is the only thing I think that could pop it out. I assume the most common way to have excess pressure is to overfill with oil. I am meticulous about oil level so this cannot be it. I tapped the fitting back in and the connection is solid, which only ads to the mystery.

The crankcase vent is fine. I checked all the oil lines and vent houses and nothing else appears out of wack or loose.