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drjon

What's it mean when the crankcase is pressurized???

5 posts in this topic

So on the new to me 2000 XR600R I just got a couple of days ago I noticed that the hose coming out of the crankcase is blowing air out at me. What the h*ll is that? Is it normal? Bike has a Wiseco 11.5:1 piston in it. Bike doensn't smoke out the tailpipe or anything and feels ok.

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A certain amount of crankcase pressure (blowby) is normal. If there is a lot of pressure accompanied by oil vapor and oil dripping from the tube, that is excessive and indicates worn piston or rings that is allowing combustion pressure into the crankcase. It is a good idea to use a filter on the breather tube. I mount the filters high in the frame above the carburetor area, this prevents dust/dirt/crud and water from entering the crankcase.

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A certain amount of crankcase pressure (blowby) is normal. If there is a lot of pressure accompanied by oil vapor and oil dripping from the tube, that is excessive and indicates worn piston or rings that is allowing combustion pressure into the crankcase. It is a good idea to use a filter on the breather tube. I mount the filters high in the frame above the carburetor area, this prevents dust/dirt/crud and water from entering the crankcase.

Mine does it (both of them) and it is normal if there isn;t like you said, allot of oil or crud comming out. Mine blows wispy air out with the piston stroke, and is totally clean. But it happens whenever it is running. please tell me thats normnal.

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Yes it's normal. Except for the breather the cases are sealed. When the piston goes up the crankcase volume increases by 600cc and it sucks in air. When the piston comes down, that 600cc of air is forced out. Any blow by increases what comes out. When the blow by gets to be too much, oil will get blown out the breather. Then it's time for some new rings.

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