OK guys, just wanted to share - Im finally done with setting the float level and I made myself a good tool out of LEGO. Perhaps someone might find it useful. The width of a "1 by x" LEGO brick is 7,8 mm, which is a good measurement to setup your float.
1) place the carb horizontally, so that the float hinge is up and float is hanging down. start slowly rotating the carb, until the tang of the float rests on the needle valve without compressing the spring.
2) doublecheck, that needle valve is closed in this position and that spring inside the needle valve is not compressed - do that by pressing the floats lightly and make sure there is no movement of a needle valve, but you should see a spring action, as the tang presses against the spring.
3) apply the LEGO tool to both sides of the float, by pressing the white bricks on the carburetor edge of the float chamber.
If the float is in position described in #1 and your float highest point is just touching the blue LEGO plate (without compressing the spring], your float level is good to go and is set precisely to 7.8mm from carb body to the lowest float edge.
I have personally set to approx 8.0 - 8.2 mm (meaning when LEGO gage applied, the float was compressed by cca 0.2-0.4 mm) and riding is good.
Maybe this might help someone.