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Water in engine oil

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I was riding my '99 YZF400 in a very wet location a couple of weekends ago and stuck it in a hole up to the lower section of the engine. The motor immediately died. We got the bike out and I was able to start it back up after about 10 minutes of kicking. Bike thereafter ran fine the rest of the day.

I got home that evening and cleaned the bike up. Checked the oil and it was milky. I flushed it with some regular oil and continued to do so for another 4 flushes until it came clean. At that time I went back with a new filter and Motorex. Air filter was slightly dirty but did not appear to be wet. I service air filter after most every ride.

I have had this happen once previously and cannot figure out how the water is getting in the engine. Keep me straight here. My theory is that it is not going thru the breather as it would have to get past the rings. Could it be going thru the crankcase ventilation tube? If so, is there an alternative routing for the tube?

Can anyone help me out here? I want to avoid this happening in the future.



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Yep your crankcase hose sucked up the water - never stop in a water/mud hole up to the bottom frame rails - you can reroute hose to the airfilter boot or cavity. I would change oil immediately and it may take up to 3 oil changes to get all water as well as sand etc.. out - change oil filters. I had this same thing happen on my WR several years ago.

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OK, thanks for the information.

Did you drill into the side of the breather housing and route the hose thru the hole and apply silicone or a sealer? Or would a better way be to simply route on the outside of the housing alongside the drain tube?


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An even simpler solution is to take a sharp blade, like an X-Acto, and cut a short slit in the backside of the breather hose at about the level of the cam cover/head joint. Cut the slit at a 30-45 degree angle, and no more than 3/8" long. This will allow the hose to function normally in most cases, but when it tries to raise a column of water up to the head, the vacuum will pull air through the slit instead.

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