Noise and tight spot in OHV 31P777

Broke a rod in a OHV 31P777 Briggs engine. Honed and washed block polished crank and miked. Did complete valve job and installed new rod and torqued. Re-assembled engine and when I spin it it has a tight spot. If I turn engine in reverse direction and then forward again it goes past the tight spot and spins free for a complete revolution then gets tight again. I fired engine and it had a distink wrap and I shut off right away. Any ideas at what is causing this ? I worked on engines for years but not one with the big counter weight in it. thanks