Walker CJ55 Motor

The motor in my CJ55 has a constant thumping (tapping) noise that vibrates the entire table ever so slightly. I notice a tiny bit of slack in the belt pulley, and when I lift up on it, it runs smooth. As soon as I let go, it drops a bit and the thumping begins again. There's no way to get inside the motor without drilling out the pins that hold it together. Does anyone know where I can get a replacement motor that isn't too expensive? I've seen the Origin motor, but I'd like to keep the cost down. Thanks for your help!