Re-routing the Rocker Cover Breather Lines
 
I have to say that I have never had any significant issue with the rocker cover breather lines dumping oil in my throttle body.  I did this mod partly because I just don't like the idea of dumping oil mist into the throttle body, and partly because I wanted to be able to track how much oil was venting out of the top end.  In the end, I confirmed that on a properly operating XR, no significant oil comes out of these lines.  The majority of the fluid caught in the catch can - a few tablespoons per month or so - is simply condensation.  The water is gummed up from oil mist/vapor which blows into it.
 
I looked around for a breather can that I might want to hang on the XR1200, but couldn't find one I liked.  I wanted it to be accessible, durable and to accept separate lines from each rocker cover.  In the end I made this one.  The body is aluminum.  The bottom unscrews to dump any accumulated oil.  And, the top is a K&N breather filter to let any excess pressure vent to the air.
 
The tubes run upwards  from the rocker covers toward the backbone of the frame and over the engine toward the front of the bike through over-sized hoses, and then drop down to the can.

Here is a look at how I re-routed the rocker cover breather lines which ordinarily run into the air cleaner to burn the vented crankcase air, to external breather lines...

 
 
Below is a picture of the breather catch can on my XR1200.



A view of my custom breather can
Breather1_resized.JPG

 
And the below picture is an alternate view of the breather catch can that I made.


Alternate view of breather can
Breather2_resized.JPG



Here is a bit of a stand-off view of the breather can, showing its postion.  The P-clamp attaches through a hole in an existing mounting bracket on the XR1200 frame.

 

Breather on XR1200
Breather-fullview_resized.JPG


 
There is no need to put air-valves in these breather tubes since each rocker cover has a one-way umbrella valve built in to the rocker cover.  Air flow through these breather hoses is already one-way - and air can not re-enter the engine through them.
 
For a look at where the lines attack to the rocker covers, click here.

 
Oil Catch bottle for the Oil Tank Overflow

While the rocker cover breather lines really should not pass any significant oil, the breather line that connects the oil tank to the engine case will pass quite a bit of oil when the engine is rev'ving.  I also re-routed these lines externally.
  Click here to see how I did this one.
 

Conclusion

As far as oil collection goes, with this mod I trapped less than a tablespoon of oil per 2,000 miles - but did collect a bit of condensed water vapor.  Granted, a Harley engine with venting problems can push out much more oil than this, but my oil mist venting should be typical of a properly functioning HD engine.  Later I ended up removing this catch can and just venting the moist air to the ground - but for those who like a catch can, the above shows how one can be done.



















The catch can is made from the body of a "C" cell Maglite, cut to length, and with a K&N breather filter fit to the top.  I drilled and tapped it the cylinder for hose-barb fittings.  It is really pretty simple - although overkill since oil really shouldn't come out of these lines.


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