Noise and tight spot in OHV 31P777

[Quick Wrench]

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

 

[Rivets]

This manual might be of help if you don't have it yet. Something is not assembled correctly and the first thing I would check is the direction the connecting rod is attached to the crankshaft. If installed the wrong way, it will hit the bottom of the cylinder wall.

https://doc-0g-5o-docs.googleuserco...253/*/0B6NaqjIxWV1ybEN0LWo3azl6OUU?e=download

 

[Tinkerer200]

" first thing I would check is the direction the connecting rod is attached to the crankshaft. If installed the wrong way, it will hit the bottom of the cylinder wall."

I don't believe this fits the symptoms he mentions but a slipped valve guide could. Valve guide should not exceed 1/8" above head casting. Valve spring keeper MAY be hitting the top of the valve guide.

Walt Conner

 

[motoman]

Is the crank balanced like it (presumably) was? Did you check the crank for alignment after main caps i.e., did it spin freely by hand? Did you surface the head (piston slap?), or use a new piston (pin to top dim)? Was new rod big end to pin distance the same?

 

[Tinkerer200]

I am very interested in what was found on this.

Walt Conner