Some common problems are caused because-

They need low nitro fuel...

Most of them need a cold plug...

They need a very long break-in, probably a gallon before they really start running good. Adjusting them before this and trying to lean them out is a big mistake. Just "running a couple tanks through" is not a proper break-in.

Broken-in right with the right fuel, plug, prop, and mixture, most of them have more power than most of the other engine in their class.

There is nothing wrong with most of them. There were some bad carbs and bad mufflers, but those problems are and have been resolved.

Another problem with them was that they came with instructions that were completely wrong for them. They recommended 15% fuel, the wrong plugs, and the wrong break-in technique. The engines come from...uhh...can't remember. Russia? All I remember is that the instructions were written by a completely different manufacturer here in the U.S. for them and they were wrong...

Anybody else have any clue what I'm talking about?