I think that cams can effect this setup greatly. My 836 screeeems.....this guy that built mine (in the late '70s), had an area cam wizzard weld and re-grinde the cam to some home-spun spec. Even with '76 carbs, it rocks....and I've ridden many fast bikes. Even has better than average bottom end torque. 0-60, about 4 seconds, but I admit....it's got 15 / "43" sprokets. 15/41 was stock in '76. Still do 120 or more though. 7200 rpms breaks the rear tire loose in the 1st three gears, and 85 to 120 on this bike is amazing!!
Some makes of cams are better than others. Ask some people around here what they've tried and how they liked it.