Do you use a proform carb???
had two 750doublepumpers
mine worked ok no problems with it as a singlecarb, worked well with two of them on the tunnelram aswell but i dont have any timeslips to prove it.
one thing to watch out with on them is that the idlemixturescrews they like to unscrew from the meteringblocks, solved it with some springs stolen from pens.