My engine is os 46. I mixed 20% castor 80% Methanol. the engine was running well but when the plane flying for a few minutes the engine burbles, stumbles and dies many times.
I found bubbles in fuel through engine tube which make engine die. How can we remove these bubbles?
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thanks

If the engine has a rear mounted needle valve then check to see if the bubbles only appear after the needle valve. If they're coming directly from the tank then check the fuel feed line for any splits or pin holes both inside and outside the tank. From what you've said there may be a split on the inside of the tank and when the level drops during flight it gets uncovered and draws air. If everything seems ok then it could be the fuel foaming from vibration. Make sure the tank is cushioned all around with foam padding and not touching any wood. If none of this helps then add one short squirt of Armorall to a gallon of fuel.