I have a 2013 Yamaha YZ450F that has a few drops of water coming out of the vent hose that comes out of the valve cover. No water in oil and no oil in water. There's a little weep hole in a small chamber right above the water inlet/outlet. That chamber is also sealed off by the valve cover gasket, so I'm assuming that it's coming out of there, but I have no idea where that hole goes to. I'm attaching pictures from the top of the head and the underside of the valve cover. I road raced this thing a few times and never had any problems with it. Here recently I've been racing flat track with it, which means high revs over and over. Could it just be some high pressure relief for the water to come out and it's normal?
Not just a crank case breather? The gasket is open to the other portion as well. Dirt bikes are offroad so they don't need the emissions crap on them. Mine blows a little bit of snot every couple of rides, i don't ride in the water either, just MX tracks.
The breather hose is direct from the crankcase to atmosphere. I would guess that any water is condensation from heating and cooling in that part of the engine. Unless you have milkshake in the crankcase, then don't worry about it. The only place where you need to be a little concerned is the water pump weep hole. When you get water (coolant) out of that, change the seal and waterpump shaft at the same time. I raced a YZ426, and the advice I got from TDub was that at sustained RPMs the YZ motor would pump oil out the breather on longer tracks, so you want to build an oil recovery system, which I think it was Graves who sold one for the newer YZ/WR engines. Otherwise fairly bullet proof.
My CRF manual states a drip here and there out of the weep hole is normal, and i do get a drip every once in a while.
Thanks guys. So the little hole in the head goes all the way down to the crank case? Makes sense, seeing as it's the only vent line on the motor. The time that it did happen was at an indoor flat track race and it was cold as shit in the pits. Came off track and put it on the center stand. A little while later I noticed a few wet spots on the stand. Squeezed the vent tube and there was still just a little water in it. I'm just talking drops, nothing heavy. Drained the water and oil and neither were contaminated. Even took the valve cover off to inspect and there was no sign of water up there. Just wanted to make sure that it was normal and that I wouldn't have a catastrophical failure at a race this weekend.
Maybe, maybe not. Look close at the gasket, it doesn't seal on the web between the two sections there. Does the left section open up into the head space? If so that would be the crankcase.
