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No Compression on either cylinder, Craftsman (917.270752)18.5 Hp Lawn tractor. Briggs and stratton engin (407777-0121-E5). what would cause no compression on both cylinders? I have verified on one cylinder that it appears the valves are seating as seen from rocker area.

Two broke piston rods is a possible.

I will check that, the engine turns easy, no unusual noises.

Are the valves moving ?
had more than one come in being diagnosed as broken con rods when the actual problem was the flywheel has come loose & was not turning the crankshaft

I did assumed that since he posted the valves appears to be seating that the rockers are moving hence the crankshaft moving.