Thank you guys for your much appreciated comments.

Firstly I will let the fuel settle for a half hour or so to allow any aeration to clear, then change the Orbit type clunk (which have worked fine on several other models). See how we go. The bubbles are extremely small, and between the header and the fuel pump, so perhaps I am being paranoid and worrying about nothing. That said I am getting rather ratty after the firece storms and weather (250 ml of rain in two days) we have had here in the last week causing our field to be under several feet of water, stopping all flying, and no power for three days !

Thank you again,

David.