Gentelmen.
In my earlier messageI mentioned vibration as the cause of fuel foaming. The foaming is inside the motor not the fuel tank. I have not seen airbubles in the fuel lines at any time weather bench running or in the plane itself.
Glow fuel weather it be Cool Power or Omega will attract moisture from the air. All motors have some fuel resdue left behind even when run dry of fuel. That is why the bearings rust out, minutly at first but will get worse asthe motor is used.
Myself and two friends have had this problem with the OS 120, OS140RX and myself with OS160FX. Changing to stainles or ceramic berings cured the eratic tuning problem.
Today I had 4 flights and like I said before.....beautiful
Kiwipaul</p>