Chocky,

If your engine will run "all day" when it's on the ground, either in a model or on a test stand, then there's nothing wrong with the engine. If the problem happens onlyl in the air, then the problem source is somewhere in the airframe/fuel system/mount/engine combination.

Usually, vibration-induced fuel foaming is the most common reason an engine will run for a while and then quit. It's overheating from being too lean. The fuel's not affected when the model's on the ground because your hands and the ground restrain the vibration modes of the model.

If the engine won't run right on a test stand, then it needs to be carefully checked to see what might be wrong.

The O.S. Max LA-series engines don't have any particular problems inherent to them. If the piston/liner fit has become loose, it's most likely that the engine's had an overheat at some time. Since your engine's quitting shortly into a flight, that's likely. Locating the cause can take some detective work.

If you believe the engine, itself is at fault, please send it to us for inspection/