Was surfing through the mothership's mainframe (aka AmericanChampionAircraft.com) and noticed something in an FAQ response that I've missed up until now. It has to do with the fuel caps, here's the Q & A copied from American Champion's website;
My fuel caps are super hard to open, we think maybe the wrong gaskets were put in the caps when I was painting the plane. But I know for sure I didn't apply fuel lube to both sides of the gaskets before installing them. Anyone try this and did it make any difference? I'll be by the hangar over the weekend and will give this a try but it smacked me in the head when I saw it and so, IMHO, it deserved a share with y'all.Fuel burns unevenly from the wing tanks, what's wrong?
An imbalance of up to 1/4 tank is normal; a difference of more than 1/4 tank indicates a problem with the fuel system or rigging.
1. Verify the condition of fuel cap gaskets; a cracked or leaking gasket will cause a pressure difference between the fuel tanks. Troubleshoot by swapping the left and right fuel caps. The imbalance will follow the leaking cap. Replace the cap gaskets if necessary. Use a small amount of fuel lube on both faces of the gasket to improve the seal and ease of installation. EZ-Turn Lubricant (Aircraft Spruce, P/N 09-00306) or equivalent fuel lube is recommended.
2. Verify check valve function with fuel quantities of 1/2 tank or less. Remove one fuel cap and apply lung pressure to the under wing vent. The check valve should release and vent into the tank (some chattering is normal). Apply suction to the under-wing vent, the valve should allow for expansion in reverse. There should be a substantial decrease in the flow out of the tank. Repeat function test for the opposite check valve. If there is a noticeable difference in flow or pressure between the tanks, replace the check valves with a matched set.
3. Parking on a slope, sustained uncoordinated flight, etc., will cause fuel imbalance. In normal cruise the wings should be an equal distance above the horizon with no yaw present. If the airplane flies wing low or aileron/rudder pressure is necessary to maintain straight and level flight, rig in accordance with the following question.