Don't give up... it's always something small.

First, is this only happening with 1/4 of a tank?

If so it is as I described above, and you may want to set your timer so as to not let the engine run so low.

Another option is a bigger tank or as others have stated a helicopter "header" tank cures the fuel flow problem.


If this happens at all tank levels, could there be something in the carb itself.

For instance some of the Evolution engines have rather weak springs that are supposed to keep the low speed needle pushed away from the high speed needle receptacle.

The springs used are much too weak sometimes causing the mixtures to go off when the plane is sideways in flight, etc.

Changing the carb or putting on heaver springs frequently cures this.


When you see air in the line, do you see on large bubble or many small ones?

If the latter try one of those sintered ( sp? ) Dubro clunks that help eliminate fuel foaming.


Under what situations does the engine run correctly?