From the Desmotimes site:
"NOTE: If you try to turn the motor over with the spark plugs installed, you will shear off the mating tangs on the front of the tool."
The engines should easily turn with one hand, escepially with the tool Desmo Times sells (the Dennis Stubblefield tool is fairly stout). If anyone ever feels the need to use 2 hands, check the plugs: they should removed.
Likewise, the engine turning tool should be removed before running the engine (a truly unique and unexpected expierence!)