While you wait for answers, we may have found some information which could help you.
Click here for Carb Adjustment Adjust
Screaming tiller?
Sears self propel lawnmower and the front wheels do not move?
transmission sears 917.2555581?
Mower cranks when primed, but after running a second or two dies?
Problems starting Lawn tractor (Sears Craftman)?
How do I set the float level in my carb?