if the chain needs replacing, odds are that the sprockets do as well.
I would not replace an original big heavy 630 chain, if the bike has not already been converted, convert to a pair of 530 sprockets and any good quality 530 chain.
some folks are still keen on non O ring chain and use a drip oiler, too messy for my tastes, otherwise I would probably just use a high quality non sealed chain, but I don't want to cope with the amount of cleaning a non sealed drive chain makes necessary.
other folks insist on riveting their chain together after cutting to length, I like to be able to more easily remove a drive chain so I use a master link, with the retaining clip pointed the correct way and smeared with a bit of silicone for extra piece of mind.
hopefully AndyChain comes along and educates us on the latest and greatest in drive chains.
in the meantime here is a very short writeup of the difference's between non O ring, O ring, and X ring chains.
http://www.biketorqueracing.co.uk/btr-tech-station/btr-tech-station-chain-and-sprockets/o-ring-and-x-ring-chains
For my Kawasaki ZX 14 to reduce friction I am using ceramic wheel bearings, the best X ring chain I could find, etc., as I am still hoping to break 200 mph on the Salt Flats and I am looking for every fractional improvement and supposedly the X ring chain is much lower friction than an O ring chain, while still keeping lubrication in. Another school of thought is to just use non sealed drive chain for salt flats use and then discard them after a few runs before the salt has a chance to eat them.
For my three Laverda triples, two have good quality O ring 530 chains supplied by Wolfgang Haerter with new 530 sprockets, the third has an excellent quality X ring 530 chain also on new 530 sprockets, I can't tell the difference in real world use between the O ring and X ring chains on the Laverda's, and I have not worn any of the three out yet.
then there is the debate on chain lubrication and what is best, almost as bad as tire or oil threads......
Paul LeClair