Originally Posted by Aceinthesky
I look at wheel main chain when I ride and it wobbles from left to right on the bottom part when I'm ridding.
Your rear sprocket is not true to the wheel, or your wheel is bent.
If you have an old front fork, stick it a vice with the dropouts pointing up and drop your wheel down on it and tighten it in so you have an eye level mount to spin your wheel.
You have to look at both planes of spin, up and down (tight chain-loose chain), and side to side (wobble)
If your wheel is true adjust your sprocket until it spins true on both planes as well.
If you have vertical up and down movement, just loosen all 9 sprocket nuts a turn or so, spin the tire until the high side is at top, lay a scrap 415 chain in the top groves and give it whap or two down with a hammer and spin it again.
When you have the vertical true you work on the horizontal wobble by tightening the 9 sprocket nuts.
A simple rule of thumb is look inside the wheel to see how the bolt ends come out past the nuts, they should all be pretty close.
You want to get these as tight as you can but stay true.