Briggs 17hp i/c twin

I have an old Simplicity 6118 which I use to plow snow only. Orginal engine broke rod and was junk. Puchase used 17 hp Briggs model 42A707 1653-01. Installed and it started right up but has a knock in the nbr 2 cylinder. The more rpm the louder the knock. Sounded like a rod knocking. Pulled engine out and took the inspection plate off. Nbr 2 rod had some play at the crank. I took the rod end cap off. Bearing looks ok with no scratches. Crank also is scratch free. Parts look almost new. I was trying to figure out what would cause this. Was looking at the rod end cap and trying to figure out if it was installed correctly. When installed the way it was removed there is play but if I turn it 180 degrees and reinstall it the play goes away. Is this possible? How can I tell for sure if the cap is installed correctly.