I have a Bobcat 50 chinese ARF ready to test fly with a Wren 44 conversion.

I fitted a felt clunk to the Dubro fuel tank but when I run the engine I get tiny bubbles from the feed line.

I'm not using an air trap.

I went hunting for the problem today & traced the problem to the clunk itself, even when fully immersed in fuel it releases tiny air bubbles.

Is this just the 'nature of the beast' with felt clunks? The engine does not seem to worry about the tiny bubbles at all, it runs perfectly at all throttle settings. - John.