Identify this engine

I got three mini bikes for $100.00. One of them, a Huskee Trail Rider, had this engine on it. I am unable to find any numbers, other than some cast numbers (13 and 1S), on it. The guy I got them from inherit them from his Father in Law. It caught fire when he rode it. I found a wasp nest in the intake valve chamber, after taking it apart. It does rotate and now has great compression. It does need a number of parts but, is doable. As can be seen in the pictures, the piston looks to be new. Same with the head gasket. The melted blob of aluminum was the carburetor! Any decals that were on the heat shields were burned off. Any help identifying this motor will be greatly appreciated. Also, I’m very sure it is not the original engine.