I have just done this on my 77F2 . I was advised by an eggspurt to go 16/48 with the 530 . Cannot remember how many links it was off the top of my head , but what I did was buy a full 530 EK o-ring chain and sprocket set for a 77-8 cb750 on e-bay . The 530 front sprocket is double shouldered and the 630 has only one . As that shoulder goes toward the motor on the 630 , it doesnt matter too much when you bolt it on . I had the extra shoulder machined off , when really all you would need is maybe a longer bolt , and possibly not even that , but if you do machine it watch out for the fact they only fit oneway . The drive shaft must have a very slight taper as my sprocket would on fit on in one direction . I also got the riveted endless chain , so no joining link . Once fitted , no clearance problems and lines up dead straight on the sprockets . Do yourself a favour and get the 530 as the 630 is an anchor chain with a ton of mass . Nowadays tech is way better so the 530 is of higher quality and strength than the 630 of old . And a little birdy told me that they will soon cease production of the 630 , so another good reason to swap , greg
