Hi Erik,
I have fitted these to various Scotts starting in 1968!
It took me several months before I became good at setting them up, but I found them to be better than the standard carb although there was a slightdifference between a full and empty tank of petrol. I fitted a constant head device to one bike by sealing the cap and allowing air in via a small bore tube which passed through the sealed cap ending about 25mm from the bottom of the tank. This worked well, but I’m not sure it was worth the effort.The biggest problem with the device was the rubbish quality of most of the components. It really needs re-engineering with decent qulaity moving “bits”. The standard version wears out quickly and in the worse case the butterfly flips over leaving you on virtually full throttle…very interesting when you are using a magneto for the sparks. Having said all that when running well they are as good as a TT Amal.
My advice for what it’s worth is to try it and if you like it ,rebuild it!
By the way Scotts need a much larger “main jet” than the four strokes.You will need to buy some small drills from about 35thou of an inch inch . I’d start at 35 and go uo graduaaly. I ended up with about 48thou if I recall. On my modified Scott i used a 35mm bored out version with a much larger central spindle so that the larger jet would shut.This came from an alcohol version used on the speedway bikes.Anyway I definitely got better mpg(5plus) and mph(5 plus) but I never did a back to back with a decent unworn carb.
John Farrar
