I have a discovery retro 60 in an Impact with a 4 ounce clunk RC tank that I have not flown yet. My problem is that with the engine running inverted (position I started it in) when you turn the nose up engine goes lean and kills. The engine runs fine as long as plane is inverted. Tank is plumbed uniflow with the uniflow open. Running FAI fuel. Any help appreciated.

I have a discovery retro 60 in an Impact with a 4 ounce clunk RC tank that I have not flown yet. My problem is that with the engine running inverted (position I started it in) when you turn the nose up engine goes lean and kills. The engine runs fine as long as plane is inverted. Tank is plumbed uniflow with the uniflow open. Running FAI fuel. Any help appreciated.

Sounds like the tank needs attention, its in the wrong place, or one of the pickup or uniflow lines could be in the wrong place, or stuck, is it a hard plumbed tank or clunk?

Check that venturi & squish clearance is set correctly.
I souldn't use a clunk tank but I doubt it's that. L

Squish 0,6mm, venturi 7,8mm.
The old Russian KC-2 plug is the best but I know that many use Enya #3.
Also, if you use synthetic oil, I recommend to test also with all-castor fuel. That is to rule out problems caused by wrong oil. L

I would take a good look at the clunk line in the tank. Maybe the clunk line is stuck where it shouldn't be. Sometimes they get stuck in the front of the tank, etc., when being transported or stored nose-down. If that's not it, I'd switch to a metal tank. Should be an easy fix. Engines really want to run, but those darned details can mess things up.  Steve

If all the clunk tank speculation turns out unfounded...From what I have seen, the DR don't like to hold an overly lean setting. If you are unfamiliar with this motor, it might just be you are not used to it. The one's I assisted launch on tend to be very fussy about the needle... You set it to where it feels like your launchers hands will go numb from the vibration and not a tick leaner or it will flame out. It will smooth out a little after take off, but not much. In order to do this, you need a light prop like Yuri makes with enough pitch to get the flight speed you want and get that needle setting.... The glow plug also has to be up to the task, make sure you have a fresh glow plug of whatever the manufacturer recommends. FAI fuel plus maybe 2 percent nitro seems to be about max in stock config, if I am not confusing my memory with the Stalker....sorry, it has been a while .
EricV

Normally the good needle setting before take-off is when engine oscillates between 2-and 4-stroke. How it works in air, depends on tank and tank position (sideways position). Pick-up tube inside tank, in rear right corner of tank, should be 5...10 mm outside the center of venturi when compared to fuselage centerline. But as you haven't flown yet, it cannot be the exact cause of your problem. But you can expect problems especially in upwind part of circle in strong wind and in overhead maneuvres if tank is mounted too much "outside", which is often the case when engine is mounted cylinder down in a narrow fuselage.
You still did not say what plug you use.
I found that the Thunderbolt plugs (big bore & 4-stroke) worked OK at first, but later the filament proved to be too flimsy to widthstand the high compression/vibration. L