will a PCV breather filter cause gasoline to build up in the oil?

Hi all - 1984 KZ700, 9500 miles. I recently installed K&N pod filters
along with a small breather filter for blowby gases. If I understand
correctly, with the stock airbox, the blowby gases are routed into the
airbox and then burned - but with this breather filter, are they just
trapped in the crankcase?

I noticed my oil level had increased significantly over the past month
and the oil also smells like fuel.

 

No, the fumes should pass through the filter, but some of the fumes
will be cool enough to condense in the cloth and mesh part of the
filter, making it oily.

If you let the breather filter get all oily, the vapors will find
another way out of the crankcase. The valve cover gaskets may weep, or
oil may ooze past the o-ring on the starter and fill up the starter
cavity.

The K&N filter you describe is best used on the valve cover of a car
engine, where the fumes can rise and the drips can fall back into the
valve cover area.

The K&N filter is not really designed to be used on a horizontal rubber
hose.

Ducati and Norton riders used to run a large diameter (about 1 inch)
clear plastic
tube from the crankcase breather all the way back past the tail light.
Too bad if a rider was following closely, he might get some oil drops
on his Snoopy googles.

Googles? What are those? Who wears Snoopy googles when they ride?

And, what is a "pudding bowl" helmet?

Leaky or stuck float valve.

 

I figured it could be a bad float valve but my carb has an overflow
tube, wouldn't excess gasoline go out the tube instead of down the carb?

 

It sounds like you believe the "overflow tube" is connected to a
standpipe in the float bowl, a brass tube that acts like the overflow
in a toilet water tank.

If you somehow pressurized that tube which you think is an overflow
tube, like, suppose you blew through the tube, where would the air
pressure go, or would the airflow stop because there is actually a
float bowl drain screw blocking flow?

One would certainly *hope* that an overflow standpipe worked properly,
but if the fuel level in the float bowls is high enough that a
standpipe drained *some* of the extra flow, it's also possible that
some of the flow would come out of the needlejet and flow down the
carburetor throat and past the intake valves and piston rings and get
into the crankcase.

The fact that your oil smells like gasoline seems to point to plenty of
gasoline getting past the float valve.

 

Is your carb overflow blocked?

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

I don't think so. if I leave my petcock on prime too long I begin to see
gasoline come out of the tubes.

 

Thats definitely true. I guess my real question was, should I get rid of
this K&N breather filter and just route the breather hose somewhere...is
the K&N filter causing any harm, or does it do any good...the bike is
finally running pretty good and is infinitely easier to service with the
pod filters so I would much rather leave them on instead of reverting to
the stock airbox.

Thanks

 

The K&N breather filter is really supposed to be mounted vertically,
not sideways.

If you cannot find a convenient place (1) to mount the K&N breather
filter in the vertical position so condensed oil fumes can run back
down into the valve cover or crankcase, just run a tube back to the low
pressure area around the license plate.

(1) By convenient, I mean a place where you can easily get to the
filter for cleaning it, without removing the gas tank or anything
that's a pain in the butt to get in and out.

 

Ok, thanks. The breather filter is pretty close to vertical right now
(its slightly sideways because the hose isn't completely straight).

Guess i'll look into the carbs.