530 chain on 42 tooth rear sprocket?

[Hinermad]

I ordered a replacement 630 chain for my GS750 and went to put it on, and it doesn't fit. I measured the current chain and apparently it's 530 chain. I counted the teeth on the rear sprocket and got 41.

Is this a thing? Most references I can find online about switching to 530 chain say to get a new sprocket with more teeth. What effect does having a smaller rear sprocket have on riding?

As far as I can tell I have three choices: get new 630 sprockets to go with the new chain, get a new 530 chain and sprockets to match, or get a new 530 chain and stick with my existing sprockets. That last option sounds the easiest, but is it going to be a prblem later?

[Nessism]

530 is the superior option. It's cheaper, lighter, more mechanically efficient, and parts are more readily available. Unless you are doing a faithful restoration, it doesn't make sense to stay with 630.

[Nessism]

Stock configuration (630)
15T front sprocket
630 chain w/96 links = 96 x .75 (distance between links) = 72 inch chain
41T rear sprocket
41/15 = 2.73 ratio

530 configuration
15T + 3T = 18T front sprocket (this size maintains the same diameter as the 15T 630 sprocket, which is important)
18T x 2.53 ratio = 49.2 (use 49T rear sprocket)
72" chain / 5/8" link length for 530 = 115.2 (use a 116 link chain (need to use even number of links))

[Hinermad]

530 is the superior option. It's cheaper, lighter, more mechanically efficient, and parts are more readily available. Unless you are doing a faithful restoration, it doesn't make sense to stay with 630.

Thanks. It should be okay with the smaller rear sprocket then?

Edit: Sorry, I didn't see your second response before I wrote that. I'll start shopping for sprockets too.

[Rob S.]

I'm very orthodox with regards to these old superbikes. I don't skimp on money or procedure. When I replaced the (630) chain on my '82 11E shortly after I acquired it, I didn't even think twice. Chain and both sprockets get replaced together, all three, all the time.

I can't do many of the things I could when I was 22. But this is something I couldn't easily do then. I love to spoil my baby.