|Click this link for the folder|
-SG- Thanks again to Ian, here's a scan of the small fold out leaflet specifically covering the twin port Models 20 and 22. The Model 20 looks like a twin port version of the Model 18 but isn't! The frame is different, the primary chain case and drive side footrest mounting are different and in the engine department, the big end has a direct oil feed via a spring loaded quill in the timing cover. And just to cap it off, the gearbox differs slightly in that it has a longer kick start axle to provide clearance for the right hand exhaust pipe. As for the Model 22, it looks like a twin port version of the ES2 - and essentially is just that! Apart from the head of course, all that I am aware of by way of a possible difference is the length of the kick start axle.