I can't take credit for this fix, DTT did it for me. It did completely solve my rattle. Attached is a pic of a carburetor spring to hold the lever from rattling. The first pic is of the entire spring. You can see one end of the spring attached to the frame (on the right side of the pic) and the other to the bottom of the shifter linkage (on the left side of the pic). The second pic shows the spring attached to the shifter linkage. There is a hole in the bottom corner of the linkage that was used to attach the spring.
T-Bone