new here and to norton

the extra effect being dissucssed is only noticed on fast off idle throttle snaps while going slowish trotting to running speeds not much difference on paved road normal use if throttle already opened much but the easy tedium to do so it kind of fun if nothing else to do with your otherwise fuly fettered Commando and may only be noticed if carb 32 mm.

From jetting-932-amals-850-comando-t19424-30.html#p252701

"Even more than displacement (750 vs 850) a major factor in proper carb set up is intake and exhaust configuration. Early 850's had virtually the same air cleaner and muffler arrangement as 750's had. The major difference was the cross-over in the 850 header system and "mutes" (baffles to us) in the peashooters. Yet many early 850 Amals had standard spray bars too. (Go ahead ask me how I know this!)

The notched Spray bar was introduced to cope with the horrifying flat spot that came along with the (mandatory EPA) fitment of this equipment! Essentially... our government required a "pass a vehicle" roll-on test from 40mph. The Amals with standard spray bars could not pass this test. Cracking the throttle open at 40mph led to virtually nil acceleration. Working with Alan Lines at Amal led to the discovery and implementation of the notched spay bars as an effective "cure".

Exactly how the fitment of a head pipe cross-over and baffles would cause a two-stroke-like "short, sharp drop in vacuum" I can't say... although the cross-over probably had more effect than is generally recognized, since it effectively made the head pipes function more like a high-volume, big-bore header. (It might also circumvent the lean/rich argument, in the sense that the notched set-up was used to simply extend and flatten out, what was a short and sharp drop.)"