Originally the Rotax carb was 5.2 g and 30/30 jets with a K27 needle, then later the 3.2g 60/60 K98 option was available.The idle jets have little effect at racing revs, I guess that the 5.2g float sat lower in the fuel and provided more displacement.The light floats less displacement- less pressure hence the need for larger jet sizes. Float height will change the level of fuel and pressure in the carb, higher richer , lower leaner, So along with main jet, needle type and clip position, venturi size these are for carb tuning parameters. We tend to run 3.2g floats K98 on p2 or p3 and I think our float height is about 5mm. I have heard it mentioned that the heavy floats are better at tight twisty circuits.
someone probably tell you that this is a load of bull but it is my understanding as a relative simpleton
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