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...
is a picture of the breather catch
can on my XR1200.
view of my custom breather
below picture is an alternate view
of the breather catch can that I
view of breather can
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
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
For a look at
where the lines attack to the rocker
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.
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
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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Harley Davidson Motor Company.