flight risk....yoiu say the fuel is percolating (boiling?) when the engine stopped. That indicates to me that the crankcase housing around the crankshaft is overheating (and possibly the rest of the engine as well). A plain bearing engine like the LA needs a minimum of 20% oil and strictly speaking all or most should be castor. Most RC fuels have 18% oil but a couple are actually only about 16% because of the way they mix it. Get a good brand of fuel that clearly says on the label just what's in it and how much, then maybe add a bit of castor to be on the safe side (22% oil is ideal).