Does crank vent system rely on carb vacuum...

[Hawkins]

... or is the crankcase pressurized enuff by blowby gases to force it through a PCV vave and filter? I want to remove all that jazz from the airbox and just let it vent to to the atmosphere.

[XSPastor]

The idea of the vent tube routing to the carbs isn't so much to help with crankcase pressure, it's more of a way release pressure and to burn any blow-by gasses by routing them back to the carbs. The engine will run just fine with a filter on the end of the tube but if your engine is worn and blow-by is excessive, I would think that you might need to clean that filter quite often. The pod guys can give you ideas about what they did with their vent tube - I've still got the stock airbox.

[Hawkins]

yeah, the original engine in my bike wore out, and all the blowby was frothing the oil, causing an awful mess in the carbs. I used a filter then, but I really had no other choice at the time. I'm doubtful it needs to be connected to the carbs, as you said, but nice to get opinions from fellow xsives. I'm thinkin that burning the crank vapors is just an emissions thing.

[trbig]

I just stuck a small filter on the end of the hose and tucked it back over the back side of the motor. One of the other motors I had had quite a bit of blow-by, and you could see the steam/smoke coming out from under the bike at stops. I kept waiting for the "Dude!! Your bike is on fire!" from an adjacent vehicle.

Just for your info though.. there is no PCV valve on these bikes.

Tod

[Hawkins]

Just for your info though.. there is no PCV valve on these bikes.

Tod

no, I know, I was thinking of using either a filter or a pcv valve at the end of the hose when I disconnect it. I figure the PCV valve, if plugged in the right way around will allow the crank to vent but not allow anything back into the crankcase.

[tw1980]

I have a fresh engine and pod filters.I don't have a filter or anything.I just have the hose attached and zip tie it off up where the air box used to be.Next to my USMC guardian bell.I don't know if that is environmentally correct but it seems to work just fine. Terry

[trbig]

It's been discussed on here not to use a PCV valve on there. If it gets clogged.. which they are prone to do with much buildup at all... that it could build up excessive pressures and blow a gasket or such. Just a suggestion.

Tod

[DGXSER]

Hey Terry,

The only reason a filter is put on is to keep little critters from crawling into that warm moist hole and making a home, or a natural plug! From there....See TRBig's statement above.

[tw1980]

dgxser

ah-ha that makes sence.I'll pick up a filter before I develop a cockroch plug. Thanks Terry

[dbeardslee]

I put a pcv valve on mine a couple weeks ago. It's supposed to create a small negative pressure inside the crankcase which in turn is supposed to help with oil consumption. Mikes XS sells one, and they claim a horsepower increase as well, albeit a small increase. Defnitely want to watch that little sucker though as too much pressure in the crankcase can be bad for seals, gaskets, etc.

[John]

If you want to use the PCV properly, then you could T together some vacuum lines from all four vacuum nipples on the intake boots, and attach the vacuum line to the vacuum port on the PCV and stick the big end in a siutable size of hose. That may work.

[dbeardslee]

The whole point of a pcv valve is to keep the pressure from building up inside the crankase, and they recirculate the gasses back into the fuel system - mostly so your car doesn't smell like oil. That usually happens on the other side of the carbs before the fuel and air are mixed, and is handled on XS's by the stock airbox breather arrangement. If you put it on the carb taps I think you could wind up with some unpredictable stuff happening.