I have the same peoblem with the craftsman electric chain saw. I checked the gear, it is in good condition and runs ok withount the cain. But when I run it with the chain, the engine is running but the chain does not move. The chain tension is ok, chain can be move in the guide bar by hand, when the chainsaw is not connected to power.
I think the chain saw has some other problems. It will cost more to get it fixed from SEARS -- Useless !
j, March 2010