The .50SX is a ringed engine...

While I recommend that ringed engines too be run on fuel that contains a reasonable measure of castor oil; for AB(X) engines I see it as absolutely imperative!

Please post a couple of photos of the cowl you have... It seems the immediate problem you encountered, was overheating.
You did not make sure there is a positive cooling flow around the engine's cylinder and head.

It isn't enough to provide a entry hole and an exit hole... Air must be directed, if necessary, using baffles glued to the inside of the cowl/engine compartment, so that as it is thrown into the cowl by the prop, it flows only toward and around the cylinder and head, before being drawn out, through a twice-trice as large exit, at the rear of the cowl.

Even hundreds of CFM flowing through the cowl, could still leave the engine overheating in stagnant air, so flow must be forced over the engine.


You're lucky it is still with us...