Steering linkage is worn causing it to be out of adjustment. Without replacement of worn parts, it is pretty hard to set them. Even if you do get it set, it won't stay long before it creeps again.
Hi, I have a 742B and this was one of the early issues that I tackled. Tazza and the others on this forum were a great help.http://users.tpg.com.au/tazza_/Steering%20Adjustment.jpg