So I was working on my bike and noticed how tight it was on part of the stroke. It when from 1/2 of play to, very tight. Spinning the cranks by hand, I noticed the tighting and loosening throught the stoke. It didn't feel smooth at all. So I studied how the chain (low end sliver Izumi) was sitting on the chain ring (a really nice 42t TA) and saw it sat lower in the teeth at a certain point on the ring (where it was loose in the stroke).
I visually marked where that piont was on the ring and removed then rotated the chain so it engaged at a different spot than before. The loose/ tight part move with the chain. With some work I got it to feel much smoother.
I would take this to mean my chain is slightly irregular. I would challenge ya'll to experiment doing the same and see if cheap chain are more prone to this. I'll be looking at a new chain soon to see a difference as well. I need a half link right now so the Shadow Conspiracy would be nice for the symmetrical look, but a NJS might be a better choice for quality.
What this means is that your chainring is not round, or it is mounted off-center. You can loosen the chainring bolts slightly and tap on the chain to center it. If you have a cheaper chainring it is probably slightly oval, which should not make a big difference while riding but will definitly be noticable to the eye.
again...ring is new and one of the best I've seen and is true and centered. The chain tensioned on one part of the ring. I removed and rotated the chain, and it tensioned on a diffferent part of the ring.
The cog was a new duraAce. I'll have to check that as well I guess.