The hole on the exhaust side of the cylinder was for exhaust gas recirculation (EGR) for a pollution situation.

The decompression valve was on the intake side of the cylinder on the electric start models. This is a 1/8" npt threaded hole that you put a pipe plug into for model airplane use. The non electric start versions rarely even have a boss for the hole on the intake side.

The electric start ones had a 12v speed 400 type motor as the starter. They were not the most successful venture that Homelite ever made. They were rather rare.

Jim