I supply a full set of 20 o'rings in Viton to rebuild the B4 carbs, they are £15 posted to the USA.
I've had fast delivery from http://www.theoringstore.com/ I found that the larger float o-ring (listed here as 7.5 x 1.5) can be replaced with 7.1 x 1.6 and it has slightly more snug fit (which is a good thing).
I am thinking of buying from there also. In the FAQ, the o-ring sizes are listed as:Emulsion tube: 10x1Pilot air screw: 3x1Floats: 5.5x1.5 and 7.5x1.5Diaphram lid: 4x1I assume that means a 1.0 mm cross section and the other number is the width? I just want to be sure before ordering. Thanks guys.