Webb,
It gets a bit dirty, but not a ton more than normal. To be honest, it seems to wet the normal oil on the belly enough that it all comes off a little easier. Makes it all kind of a fine, misty deposit. YMMV, of course! The tailwheel is my "mixture control indicator". It gets dirty no matter what, but if it drips on the hangar floor, I need to close the valve a bit.
OBTW, the smoke is worth it!!
Ya know, I still haven't had a JAN overnight since we talked about getting together to see your build...and now you've been flying for a couple years! Will still call if I get one, so we can have that cigar and check out your plane...if you're still game!!
That's another kind of smokin', eh!!
Cheers,
Bob