Hi Dave,

Today at the field I experienced a strange phenomenon. I run my Ys a bit on the rich side. After take off the engine becomes extremely rich and gradually leans out to prior take off level. this takes about 40 sec, making the take off dangerous following the loss of power.( During the rest of the flight the engine is perfect.)

Any clues?
Thanks
Brian

Who knows? Could be a tank that bleeds pressure periodically, but without seeing your entire install in person, I just don't know.

You don't mention fuel, exhaust system or plug so there isn't much to work with here.

Hi Dave,
I am using an OS #8 plug, YS muffler, 10X7 Graupner prop and Morgan Heli fuel 15% Nitro,
The fuel tank is a Dubro 12 OZ.
I double checked the fuel tank and it's fine. Could it be a temperture problem?
Thanks
Brian

Maybe it's just too lean.