I have two briggs stratton 16.5 ohv model 313777 type 0112-e1 code ooo404ze that will not start. Hard to turn over . Battery =fuel-starter are good . I have changed the fly wheel key and tried to adjust valves. What could cause two engines to do same thing? Engine turns fine with plug removed.

I would go back to the valves. Did you go to TDC and turn 1/4" past TDC to adjust the valves?

I have two briggs stratton 16.5 ohv model 313777 type 0112-e1 code ooo404ze that will not start. hard to turn over . battery =fuel-starter are good . I have changed the fly wheel key and tryed to adjust valves. What could cause two engines to do same thing? engine turns fine with plug removed.
I had problems where it spun to the Compression point and stalled out. Appearing slow! Once past that it spun hard again till it hit the compression stroke. If this is what you are having here's a solution I used successfully. Remove the cover from the valves. A wrench and Star screwdriver are needed to adjust and lock the valves and a feeler gauge between .003-.005 inch. Clearance should be measured just as the spark magnet moves past TDC, just off the magnet. Be sure it's the compression stroke and not the Exhaust stroke. Adjust valves, both at this point. Info. Tilting the engine such that oil gravitates away from the Valve cover helps but you shouldn't loose much anyway, use a big rag. Replace cover,and plug if you removed it. Should spin much better now. Good luck. Edd