I have a craftsman lt 1000 w/brigs&straton 17 horse engine i replaced battery & starter but the engine turns over slowly but wont start the battery is fully chaged Im a good mechanic but this has me stumped

It sounds like the compression release is not working,it works by opening the exhaust valve during engine cranking.For the compression release to work the valves have to be adjusted,especially after the engine is broken in.Set the engine to top dead center on the compression stroke,the exhaust valve should be set to .004 and the intake to .002. I think you will find the exhaust valve is way too wide which is causing the hard crank problem.Set the valves by adjusting the nuts on the rocker arms,it should be a torx set screw located in the rocker arm.First back the torx screw out about a turn then hand tighten the rocker stud with the feeler gage in place then tighten the torx screw down to lock the setting.