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I need some opinions here

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So, ive been toying with my jetting to get the most amount of grunt for the least amount of gas and i think ive found it for now. Thats not whats bothering me. What i dont really understand is why the crankcase breather tube is plunbed right into the airbox behind the air filter recirculating that HOT,OILY air right back into the motor???&%$#@! :thumbsup: . why would you want that???I just want to cut that hose and let it vent. any thoughts would be greatly appreciated. .

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If you cut it, make sure you put a mini oiled filter on the end of the hose and mount it up high where it can't get water in it. (exactly like the slide diaphram vent hose)

Dylan

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The reason is to burn that hot oily air rather than pollute the world with it. The only source of air from the crankcase is blow-by past the rings and valve seals so it should not be very much until the engine is worn out. This was the first pollution control trick that came out on cars in the 50's.

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The reason is to burn that hot oily air rather than pollute the world with it. The only source of air from the crankcase is blow-by past the rings and valve seals so it should not be very much until the engine is worn out. This was the first pollution control trick that came out on cars in the 50's.

ahhh.. I understand now...I think my motor is getting old..cuz theres a lot of oil in my air box...Thanks

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Oil mist in the crankcase is normal. One reason to plumb the vent line to the airbox is because there is a slight vacuum in the airbox so it slowly pulls the mist and or blow by fumes out of the block. The block has to be vented because the piston going up and down changes the volume of air in the crankcase. They used to dangle that tube down near the road on old cars. The wind going by would create a venturi effect vacuum (similar to plumbing to the air box) and the oil/mist would drip out on the road. :thumbsup:

I would not jump to say that your engine is getting old just b/c you have oil in the airbox. If everything is working right you should have some in there. That is why there is a drain on the bottom of the box

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Some bikes have a little expansion bottle in this crankcase vent line. It provides a bit of a spot to let the mist separate out from the flow and drain back down into the case instead of oiling up the airbox. It's not perfect by any means but apparently it puts maybe 2/3 of the oil back into the engine that tries to flow up the tube. Even my little XR100 has a little medicine bottle sized separator in the case to airbox line. The Ducati I had used a pop bottle sized separator. So perhaps finding one and using that may help a lot. Something like an inline gas filter that you take the filter element out of may do the job. Of course you'll need to glue the outer cover back together. Just don't leave the filter intact or the oil will plug it up and try to prevent the proper flow. The separator "bulb" needs to be empty. And the line from the case should be attached on the lowest point so the oil can flow down along the inside surface of the tube.

Also if you fall a lot it's normal for some oil to puke up this line and get spread around the airbox. Or if you overoil the oiled filter then it's also normal for the airflow into the engine to shake this oil loose and mist it over the insides of the airbox. So it may not be all from your vent line.

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