chain manufacturing and metallurgy has come a long way in 30+ years. a cheapo 520 oring chain these days is as strong as a 630 chain from the 70s. back then, 630 chains were the only things rated to withstand that level of power at a decent price.

chains also used to be under an insane amount of extra stress and friction since they were non-oring and riders couldn't be trusted to regularly lube them, so the bigger the better, right?

 

^^^^^Actually, a popular modification on small, not so powerful bikes, like Ninja 250, GS 500, etc, for racing is a NON Oring chain because they have less friction than an Oring chain as long as they're properly lubricated.

 

Just a quick thank to all those who offered advice, 520 DID, -1/+1 Afam sprockets and a huge smile, much better ride now so thank you

 

Nice, enjoy ripping on it! I put a 520 on pretty much everything I ride, never have had any issues