Set up: Brodak 40 stock (newest version) factory muffler, Merlin 2005 hot plug, 11-4 wood prop, 10% nitro, Brodak 4oz uniflow wedge tank 1/8" above center line. Dubro filter, good tubing, Profile Sig Banshee, 63' lines, oat 65f.
I had a 5oz tank on it that I made and I tried re plumbing a few times but got the same problem so, I got the Brodak tank and the problem is still there.
I set the needle on the ground so it's 4 stroking with just a wisp of 2 stroke now and then. It's basically running rich then, when it takes off, it goes lean in less than a lap almost full 2 stroke. So I'm wizzing around the pattern and when I get to the square eight it starts going rich almost a full 4 stroke then it gets richer from there. I can still finish the pattern, in fact when it's running full 4 stroke it's much nicer to fly but, at the start of the flight it's a rocket ship.
I've tried allot of needle settings and it still goes lean to rich throughout the flight only leaner or richer overall depending on the needle. I tried higher pitch props but they make the plane too fast. I had an old K&B 1-L plug in there and had it set so rich on the ground it was almost cutting off and it still went too fast after launch.
I've never had a tank that goes from lean to rich through the flight but somehow I don't think it's a tank problem. Maybe it needs head shims or a smaller venturi?
MM