Small Engines (Lawn Mowers, etc.): BRIGGS & STRATTON LAWN MOWER ENGINE, briggs stratton, vertical shaft

Question
I took apart the engine, cleaned it up and put it back to gether.  It starts easily but runs really rough.  What is the procedure for adjusting the valves?  These are the 3 numbers on it 2bsys.190wh 275260 and 123k02-01315-ej04032457

Answer
I see by looking up the model number that you provided that this is a vertical shaft L head engine.  The method to adjust the valves is to place the piston 3/4" past top dead center on the compression stroke, remove the valve cover behind the carburetor and measure the clearance between the end of the valve stem and the tappet.  The reason it must be placed at 3/4" past top dead center is that this will bring the cam into a position that the compression release will not be affecting the clearance on the exhaust valve.  Hope this helps.