I have tried a few combinations on the 1200. Started with 77 heads cams and carbs in a 1000 frame. Rode it a few summers. Converted to a 1200 swingarm. With the 77 cams, it’s torque is spread out wider. It has pretty good torque down low probably due to the extra stroke of the 1200, but the cams let it pull a little higher into the rpms just like a 1000/1100.
This summer, after finding that the stock 1200 heads have just as much intake lift as the 77 (because of different rocker arm ratios, not cam lift) and more exhaust lift along with more overlap, I decided to put them on. I haven’t had much time to tune it as winter came pretty early here, but I’m pretty convinced the 84-85 heads and cams are better than the 77’s. You give up 2mm of diameter on the intake valves, but you gain some back because of the exhaust lift being greater in the 12 and probably gain some from the greater overlap.
The other part of the equation is the ports of the heads. The 1000/1100 ports are considerably bigger, but they probably don’t help until you’re approaching WOT and higher rpm. The smaller ports of the 1200 probably help more at the bottom end.
As far as performance, I think it’s just learning to shift earlier in the power bands. Your ears tell you that 1000/1100 is going faster because it’s winding out, but I think in speed the 1200 is faster at lower rpm, so you shift earlier, it doesn’t have the same pitch sound, and as far as shifting, wind out fourth gear and you’ll be going faster than anyone should on a forty year old bike.
I hope to get some different carbs on mine this spring and maybe the 1100 swingarm.