Water out of the air box?

I just bought a '04 WR450 and am in the process of stripping it down to clean/lube, and learn my way around the bike. When I removed the air filter cover water poured out, I mean there was a pint in there!


Looks to be a vent hose routed from the cylinder head into the airbox, don't know if that is were it came from or from the intake port under the seat.


Scared the crap out of me as the air filter was sitting in water. 


Is this normal?, or did the PO dump it in the middle of a stream? If left out in the rain could this happen? We have had some torrential rain here lately.  

Yes that would happen if you left it outside in the rain, which you should never do.


Your air box is suppossed to have a 'pinch drain' hose on the bottom that you empty periodically.


You need to start the motor asap and get oil spread around to prevent rust on the cylinder.

The cylinder itself is incapable of rusting.  The rings, though, are another matter. 


Before I started the engine, I would take the crankcase drain, which should be the one under the bike, pointing slightly rearward through a hole in the skid plate, loose and almost out, so as to see if water comes out of it.  If water entered the crankcases while the engine was not running, it will sit there without mixing in, or getting into the tank in the frame.  It will also be the very first thing to leak from the loose drain plug, too.  If found, change the oil:




If no water is found, and the oil looks like oil, then fire the engine let it run a minute, shut down and check the oil level and its appearance.  If water gets into the oil and mixes, it will turn the oil into a milky, foamy, "milk shake" looking mess.  Drain the whole thing immediately, replace it with something inexpensive, and change it again after 30 minutes run time.  This includes the filter.  Most people use the OEM "paper" type filters, and water will swell up and damage the filter media.

Thanks for the clarification. I may look at way to prevent that from happening in the first place.

I was running the engine prior to removal, I may squirt some oil in the spark plug hole, looks like I'll have to pull the fuel tank to do that.

I'm going change out all fluids/filters. SOP to set base line for maintaince.

I'll tear it down to the frame eventually, but certainly want to get some seat time in before.

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