Wow, that book looks a bit intense for my puny brain, Shaun! The Exup-style valves are a four-stroke thing, but you\'re right, wave scavenging effect is even more vital in two-strokes, which is why you used to see such gorgeous bits of engineering as hand-welded titanium expansion chambers on GP two-strokes.
Funnily enough, most of the understanding of two-stroke \'spannies came from an engineer working for MZ of all people (sort of the Lada of the bike world for many years) when they were at Zschopau (sp) behind the Iron Curtain in East Germany. Walter Kaaden, his name was IIRC, and he\'d developed the idea of pulse scavenging on the MZ gp racers, which from then on were unbeatable. In a proper spy thriller stylee, he defected to the West, specifically Suzuki I think, with a whole load of diagrams and tech drawings, at a neutral GP whilst his wife and kids were smuggled out of East Germany to meet up with him. MZ couldn\'t compete with the spending and developement power of the Japanese, and the two-stroke era of GPs was a Jap playground from then on in.
You\'re right, nothing much to do with rotaries, but it makes a good story. I always kinda thought of rotaries as a lot like a two stroke, but it goes roundy-roundy rather than uppy-downy, anyway :Giggle Helps me understand stuff in my feeble brain!