New sprocket / old chain?

[Rickyrebar]

When changing a 15 tooth sprocket to a 14 tooth, should you also replace the chain (worn or not)?
And vis a versa, if replacing a worn chain, should the sprocket be replaced (worn or not)?
What are the proven brands of choice in chains and sprockets?

[AndrewRRR]

If they aren't worn I wouldn't. Look on the sprocket to see if the teeth are rounded off or bent over, if so, replace it. On the chain look for play (hold it on it's side and see how far it'll bend on its own, not forcing it, if it looks like a rainbow replace it!).
I like DID o-ring chains (they call them X-ring), and sunstar sprockets.

[cals400ex]

i have never replaced my chain when tinkering with sprockets. however, i think they recommend it but if the chain is in good condition, i wouldn't do it either. now, if i wore one of the sprockets down and then replaced it, i would get a new chain because it probally needs it. however, i just tinker with my gearing and all of my stock sprockets are still in great shape.

my stock front sprocket from when my stock chain was wore down & loose

[AndrewRRR]

Yeah definately replace the chain if it's worn. I found out the hard way on my R once. I was left with a 10 1/2 tooth front sprocket and a broken case saver (luckily i had one on!).
A buddy of mine also cracked the cases on his banshee when he broke a chain. JB weld fixed it for the weekend but it did dump all the tranny oil when it happened.