I need a manual for a Yard King Model 261011X89A. The self-propel stopped working and maybe the manual can help me identify problem.

Hi,
Are you sure about the model number? Usually the first two digits are the inch cut of the machine.
Peace,
Clarke

Hi,
Well, I did some more searching and found a parts breakdown. I guess Murray changed the model numbers on the walkbehinds same time as they changed the rider designation. Below is an attached parts breakdown.
Peace,
Clarke
PS It is a variable speed machine made by AYP and the most common problem with the drive that causes your symptoms is that something is jamming the moveable sheave in the middle of the variactor.