I have a new SkyRaider Mach I with a used Evolution trainer A .46 and a 12x7 prop @ 12000 full throttle. The engine works OK at idle and 1/2 throttle.
At full throttle I have bubbles in the vent line, supply line, and carb line with consequent surging. I have replaced the line from the remote mixture to the carb and the supply line from the fuel tank to the remote mixture control. I have leak tested the tank with the vent line and the supply line attached. No leaks. I dismantled the muffler, but it was fairly clean with no blockage of the vent line. ( 31 flights since new ). When putting the plane together I changed the
restrictive aluminum tubes in the fuel tank to less restrictive brass ones. What can be causing fuel and bubbles to be in the vent line?