520 chain
 

I'm planning on putting on a 43 tooth rear sprocket over the winter. If I think it needs more I'll go down to 15 in the front (although maybe it makes sence to change the front first as I've heard that's easier. I also have heard its hard on the transmission though.)

What are the benefits to a 520 chain conversion? Do you need to even change the stock chain by going -1 +2?

-1 +2 works with stock chain...

A 520 chain is lighter, less material... Supposedly it makes for quicker response? But i doubt the weight difference makes much difference other than in your head...

So if I go 15/43 the shop can simply break & reconnect my existing chain? Its still shows "new" on the swingarm dealio, I was going to wait until it wore out.

It will always say new unless you tighten it. If it says new and has 4 inches of play its not new.