Brompton owners

I've got a six speed, which at the moment only has two and a half working gears. I can't changed between the sprockets as one constantly slips so much as to be unrideable, which may be down to the 'nudger' or possibly to the wear on the sprockets. The low gear of the three-speed up will also only work if I keep the lever pushed down.

How much of a weight difference would I notice if I just went for a two-speed wheel rather than getting the gears seen to? It's the old Sram hub gear on mine, and it also has the rack which I would happily swap for the L mudguard setup.

I bought a 2 speed wheel off here to replace my 6 speed one and there's about a kilo difference. Not much difference when riding but if you're carrying it about then it adds up.

That was my reasoning anyway.