crank case breather tube

On my 2010 450 the crankcase breather tube comes out of the valve cover and routes to the lower left side of the bike. I was checking the line and noticed that it is completely unfiltered!!!

Is this for real? If you went through a water crossing on this thing, or were riding in dusty conditions it would go right up and in there wouldn't it?

The tube is rather bike, about 1/2 to 3/4 inch inner diameter, making dirt and dust easy to fly up in there.

Think Im going to have to rig something up, unless someone tells me otherwise


Found a great thread on this issue here;

Grey you explained it well. I guess the tube has positive and negative pressure going through it both ways all the time. Water, dust and dirt will not be drawn in through a longer hose because it will probably go about halfway out and then be pushed right back out by positive pressure.

The only danger is if the tube is submerged in water or very fine sand as the engine is stalled or cranked. At very low speeds, there is actually time for the breather to pull something in during the piston upstroke.

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