I wasn't familiar with your saw but I looked at the parts diagram for it in the link below thinking there may be a replaceable drive pin or something like it that would possibly have sheared. http://www.masterparts.net/111409-01.html I didn't see any. That would indicate that the sprocket may be stripped out on the inside and would require replacement, or, that there is something stripped inside the gearcase. If you look at the diagram, the motor shaft is parallel with the handle. So to drive the sprocket gear that drives the chain, they use gears inside the housing to turn the sprocket that's at a right angle to the motor shaft. Do you follow me? It would appear from the parts diagram that if it is those internal gears, that it would require replacement of the whole motor/gear assembly ...... probably as expensive as a whole new saw!
The reason that the sprocket turns without the chain on is that there is evidently enough friction between the shaft that the sprocket mounts on, and, the sprocket. But not enough of a connection to drive the chain.
To check further, leave the saw unplugged, and use your finger to try to turn the sprocket. If it turns by hand like that, it would indicate that something is stripped out as I said. To see if it is the sprocket, remove the "Retaining Ring, 5/16" that is shown in the diagram, and inspect the inside of the sprocket. If that appears good, then it would be an internal problem and probably not worth fixing. Good luck! Ed
Answers & Comments
I wasn't familiar with your saw but I looked at the parts diagram for it in the link below thinking there may be a replaceable drive pin or something like it that would possibly have sheared.
http://www.masterparts.net/111409-01.html
I didn't see any. That would indicate that the sprocket may be stripped out on the inside and would require replacement, or, that there is something stripped inside the gearcase. If you look at the diagram, the motor shaft is parallel with the handle. So to drive the sprocket gear that drives the chain, they use gears inside the housing to turn the sprocket that's at a right angle to the motor shaft. Do you follow me? It would appear from the parts diagram that if it is those internal gears, that it would require replacement of the whole motor/gear assembly ...... probably as expensive as a whole new saw!
The reason that the sprocket turns without the chain on is that there is evidently enough friction between the shaft that the sprocket mounts on, and, the sprocket. But not enough of a connection to drive the chain.
To check further, leave the saw unplugged, and use your finger to try to turn the sprocket. If it turns by hand like that, it would indicate that something is stripped out as I said. To see if it is the sprocket, remove the "Retaining Ring, 5/16" that is shown in the diagram, and inspect the inside of the sprocket. If that appears good, then it would be an internal problem and probably not worth fixing.
Good luck!
Ed