engine goes rich

HI
I have schurnle 19 mounted on a profile with metal wedge tank lined to the center of the ventury it runs great for the first1/2 of the flight but then goes rich for the last 1/2,any ideas would be apriciated.
Thanks
DW1

NEeD to go to Muffler pressure or try a Uniflow tank ...and put the tank about 1/4" higer then your venturi ...Scott Riese

My analysis was that it started off sucking air somehow -- bubbles, most likely. It's a Perfect Wedgetank; with those, you can never be sure of anything (opinion, yes, I know). It starts off running wrong and halfway through the bubbles stop and allow it to run "normally."

Well, it sounds like a good excuse to me!

Let me make another suggestion. Maybe it is actually leaning out and sagging. Going lean is the typical way the mixture goes since the fuel pickup is almost always outboard of the spraybar. Thus a normal tank will lean out the mixture as it empties. If you start out right on the edge, the engine will slowly bein to sag, maybe fooling you into thinking it is too rich.

Try to richen the needle and see if that helps. At least you should be able to actually hear it begin to lean out, if that is the problem.