Originally Posted by
Schwinnsta
I As well as I can remember, when I first got it, it shifted from the smaller rear sprocket up to the larger by simply on move of the 2-speed shifter. For the longest time, it requires a conscious second push down to start the shift.
Not sure what "on move of the" means, but you should…
1. Clean the gunk off the derailleur: It's a well known issue on the Brompton
2. Get a new cable + housing.
Brompton shifting problems ? Ready-Made