I recently bought a tigermoth biplane and will be running a os .61 fx, however unlike my last plane ( a trainer) the engine in this one is mounted upside down. My problem is I am trying to break in the motor and am following the manual for needle turns etc. But I can't turn over the motor when its upside down, its like its got too much fuel in the chamber and is locked up, but when I turn the plane upside down so the motor is upright I can get the engine to run like a top. How or what am I doing wrong since i am following all the directions.

OS # 8 gloplug,
15% N 20 % oil fuel

Thanks Ickleboggle

You may be over priming the engine. Hopefully the tank is in the correct location in relationship to the carb sometimes that will cause the engine to flood prior to starting.

Try starting the engine without priming. If using a starter please ensure the engine turns easley it is very easy to bend the connecting rod trying to start a inverted flooded engine.

There is nothing wrong with getting a helper to hold the airplane upside down to assist in starting.

The problem is that I have gotten the engine to run when I flip the plane upside down (then the engine is upright) but as soon as I get the plane turn over (now the engine is upside down) the engine shuts off, ive tried it with the glowstick on the glowplug the whole time and with it removed once the engine is running.

You may be running too rich

Try using a glow plug with a idle bar on it.

Try pulling the engine out and bench run it upright for a few tanks to break it in. Once you are able to set the mixture for normal operation, invert it on the bench and run it. Be sure the fuel tank is at the same level in relation to the carb as it will be once it is back in the plane. Set the high and low needles on the bench and if it runs good there you should be good to go after it's reinstalled.

I have a Dymond Tiger Moth with a magnum 60 four stroke inverted on it. The low end needle had to be turned almost all the way in to get a good idle and transition. Just make sure you break the engine in before you start leaning it out and low end adjustments should be made a little at a time ( 1/8th turn) I had to spend a lot of time on my knees. I really should get an engine test stand. Good Luck.