CVO Technical > Twin Cam

Should I vent to atmosphere?

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Heavyhaul85:
Hey all. I have oil in my air filter. I believe my breathers in the rocker boxes are no good. It wouldn't bother me to change them but my gaskets aren't leaking yet. Bike has 32k miles with original gaskets. Should I run a hose and vent to atmosphere or jump in and do breathers and rocker box gaskets?

Twolanerider:
Several things will force oil.  Cylinder head breathers are only one of them.  There's a half-assed check for the breathers to see if they're work though.  Get something you can screw in to the cylinder head breather holes.  I use an old breather bolt with the head cut off (have to hold finger over the little whole in the side).  Once you've got something in the head pucker up.  Put your lips on it.

On each side you be able to suck through it but not blow through or vice versa (on the other side).  If they'll do that pretty obviously the head breathers are probably ok.  There's been a revision to the breathers since your 2000 model and the new pieces are better.  So if you're looking for a reason to do them just to be sure that could be it too.

Do a leakdown test to see how well the cylinders are sealing.  I've also seen the vent hose from the engine to the transmission case collapse internally and cause problems.  And just do the normal stuff like checking for vacuum leaks. 

Something has changed if you've got oil in the breather now and didn't before.  Before I started dumping it to atmosphere I'd like to know what was causing the change.

Heavyhaul85:
Great thanks for the tips!

johnsachs:
When I'm working on Harley heads, and the customer requests a breather mod to atmosphere. This is the method I use.
John

ultra13:
Kevin Baxter at Skunkworks has some videos on venting on you tube.

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