Walter,
The engine on the left is a Homelite 25 or 30cc. The center is a Weedeater 18cc or so. The one on the right is a McCulloch 32cc saw engine. The best of the bunch is the Homelite. The Mac will work, but has a needle bearing crank and some are hard to start. The Weedeater in the middle is not much good, as it isn't heavy enough to hold a door open and is a little heavy for the power produced.

Dave