I've had a lot of trouble with sticking floats on my '82 RS, it all started when the inside of the fuel hoses crumbled into tiny little cubes of rubber which prevented the float valve from seating. This happened a few times, I always opened the fuel taps briefly to flush any bits out after first removing the float and allowing the valve to drop out. Eventually it dawned on me that there weren't any more bits of rubber,or, indeed, any other debris getting flushed out (I was catching the flushed fuel in the float bowl and then returning it to the tank after taking out the bits) Well, it cured the problem for a while, so, what the heck, you know how it is...
Anyhow, last month as I was going through the performance for the umpteenth time (and having in the meantime installed new needles) I noticed some rough marks on the hinge pin on which the float pivots, and I remembered that they must have been caused when gripping it with a pair of pliers in the middle and sliding it out of its supports to release the float. As the sticking float was a recurring problem I had been puttng the pin back in a slightly different position with about 2mm of its end protruding to allow be to grip it and extract it with the pair of pliers more easily, with the roughness on the pin in its new position making the float stick. So after putting the pin in the electric drill and lightly holding a small file against it before replacing it it does look as if the problem has been finally resolved. It's been ok for about a month, so perhaps it might be worth you checking your pins for roughness