Thanks Barney! Both 90s have the original carbs probably, I ordered the replacement carb from Winncycles to try on the yellow 90 wich is still on holiday. The carb is the on e with the high altitude knobber and the fuel lines in the right place. If the yellow 90 doe not respond to the new carb then I know I have a different problem right.
I put another 15 miles or so on the red 90, aka Barney. Never a stumble in the rev range but a little hunting at idle. Probably hit 40 today and felt better about it than the 110. Crying shame about that. The 110 is so minty. And by the way my 110 has cdi but is still 6v.
The throttle on the yellow bike is reasonably great for what it is. The same setup on Barney is sticky. With the throttle tube removed the action is snappy, but with it back together something is lost. New cables all around. My aim is to ride the snot out of it and pin it till it blows or goes.