I've read about draining the oil and checking for flakes and what not. Has the oil level been checked? if the fuel was left on wheil bouncing down the road in the bed of a pickup, the float in the carburetor bounces too, flooding the engine. If then left to sit for a day or two, that gas seeps past the rings and into the crankcase, therefor "overfilling" it, and thinning the oil, losing lubricity. I have had small engines come in for repair over the years with this being an issue. Most of them I could drain the oil and refill to correct levels and run it. Others had thinned the oil enough, and then run it, that the piston seized. Simple and free check, pull the dipstick, check the level, and smell it for gas, then go from there. Best of luck to you both!