Tips for containing the spooge - KTM's without o-ring sealed
exhaust flanges.
First off, for all you non-KTM'ers reading this, get'cher mind
out of the gutter.  We're talking about that black oily crap
that oozes from the cylinder/pipe junction and drips out the
back of the silencer or spark arrestor.  Newer KTM's have
O-rings on the exhaust flanges, so those of you lucky
enough to have such bikes don't have to go through the
annoying rituals described below. These tips apply to the
KTM's that
do not have an O-ring exhaust flange. Without
the O-ring, the end of the pipe fits over the exhaust outlet,
metal-on-metal, with nothing keeping the black stuff from
leaking out.  Also, the pipe fits
around an exhaust flange,
which is not as effective as having the pipe fit
inside an
exhaust flange as with the newer KTM's and most Japanese
two-strokes.

Solution #1
Put a layer of red high-temperature silicone on the outside of
the exhaust outlet, put the pipe back on, and let it dry for a
day.  I would not recommend putting the silicone on the
inside of the pipe.  When you push the pipe over the exhaust
outlet, the excess silicone gets forced into the pipe, dries up,
breaks off from exhaust pressure, and then gets stuck in the
end of your spark arrestor (if you have a silencer, this is
probably not a problem because it would blow out
unobstructed).  This method will work until the pipe gets a
couple of rubs against rocks or other hard objects, and then
you'll need to re-seal the junction with more silicone.

Important tip:  clean both surfaces until they sparkle,
then
apply the silicone.

Solution #2
Convert your exhaust flange to the 250SX version that has
an O-ring.  The part numbers are:

547.05.003.000 (exhaust flange)
0770440030 (Viton O-ring for the flange)

Total cost should be about $20.

CAUTION:
I can only guaranty that this will work for the 2002 300 EXC
and MXC - for other models, use at your own risk. Also, the
O-ring flange has a smaller inside diameter than the stock
flange.  This smaller opening will improve bottom end
somewhat, but will take away some top end power and force
you to re-jet.

Spooge out the spark arrestor
No good solution here, but one that helps is replacing the
stock spark arrestor with a silencer or an FMF Turbine Core
spark arrestor.  I chose the FMF Turbine Core, which is
shorter in length than the stocker, so at least the spooge
doesn't drip onto the rear brake.
Got Spooge?