Hi,

I have a 3W 55 US engine with a supersonic pitts style muffler and a 3W 23x8 prop . The engine is mounted inverted and I have a 3W tank and the vent nipple has a tube that goes inside the fuse.
When I fly on knife edge with the carburetor up the engine reduce rpm and almost die. This phenomenon apears only with the throttle lower than 40-50 % . On high rpm it works fine. But on 3D manouvers the engine it not responding right .. rolling hariers… for example.. every time that the carburator goes up.. the engine loose rpm. I've check and change the tank.. over and over again.. no results.

Last weekend I leaned the low needle and the problem seems to reduce a little .. it only reduce rpm if the throttle is about 30% or less., but the down side is that is dificult to start the engine when is cold.

PLEASE help …!!! What is the problem ? I know in theory that the engine should run in any position because the carburator has a pump in it…

On the ground I tach 6400 rpm and I have a steady idle .. and it works greate in any position. The engine has about 30-40 litters of gas thru it and I use sintetic oil 1:40.

I wrote the problem to 3W suport and I got no answer…

How long should be the tube from vent nipple to the fuse ?

I have 2 more 3W engine 28 cc … should I espect the same problem ? Or is because the side carburator ?

Thanks !