In article , Wwj2110
wrote:

"Specifically the blade walks off of the non-driven wheel within
2 to 3 rotations of the wheel."

Sounds like 1 or both of the axles are either bent or worn. I would check
with
a straightedge over the faces of both wheels while they are tightened down
with a blade installed.
You didn't give the model #. If it is like most I have seen they
require a tire unlike the Asian imports. As some one else said, they
have to be very tight. The twisting action from the blade guides might
be the cause if it is not tight. I might be able to send you a copy of
the manual if you can find the model number. You might still be able to
get the tires from Sears. I bought some about 15 years ago.

Chuck P.