The complete Tecumseh engine repair manual is available for download in the Small Engine Repair forum. Its very thorough.
I totally agree with that, the regular briggs 3.5 horse motor is almost indestructable, I have seen them go for 2o years or more without skipping a beat, just change the oil and clean the deck and oil it every fall,. It will last forever!!! that goes for the simple old lawn tractors that use the 5 horse briggs, they will last for ever and pull over a house if they can get enough tractionI think the best push mowers have Briggs & Stratton power and no options whatsoever, just a basic side discharge non-propelled machine. All that other stuff just adds needless weight and complexity.