Can you jack the machine up and see if you can turn the wheels on the left and see if they move the same amount? They should only move a small amount as the chains take up the slack. Hopefully its a broken chain that has gotten caught, if not it sounds like your motor may have packed it in. As you mention the motor bogs down it appears you have something that is stuck, hopefully your chain, check the easiest things first.
What did it do before it stooped working? Was it slower or less powerful than the right side?