Hi there, I just a had a read of your bike while we're waiting for AintNoEasy to get his running, and noticed you said something about the chain not lining up.
77s have the wide sprocket carrier that offsets it outwards 10mm.
I've put up a photo of the 77 and earlier carriers, and what I have on my 77.
It's either me or you that have the wrong one on, but they look different on mine.
Wider carrier, smaller spacer on outside, longer greasy spacer inside, sprocket closer to swingarm.
Also the pressed metal chain catcher ring on the outside seems extra important now because there's not enough room for the chain (at least for the 630) in between the sprocket, the sprocket studs and the swingarm if the chain ever comes off, instant lockup. I've had a wheel lockup on a bike,(but not from this,) and am lucky to be alive. I'll leave mine on.