The pinch test is a momentary thing. You go to full throttle, then QUICKLY pinch the fuel to the carb and the RPM should slightly increase. If it does not, it is not right. If it dies, it's to lean. If it takes several seconds to do that, then it's very rich.. and will spit oil/fuel.

As for the low end, well, it becomes trial and error. This is a transition thing and adjustments on that low end screw are very small, likle on the order of 1/8 of a turn at a time.. very small. Make the adjustment, then run the throttle up to full. It should immediately go to full with out hesitation. If it's to rich, it will caugh and sputter as it tries to go up, all this is the burning of the excess fuel that has accumulated.

And, if it sets for a few minutes at idle, it may/will load up but this is not the transition issue. This is fairly normal and why you should run the engine up to full throttle for at least 10 seconds before taking off. This is hard to adjust properly.. getting both the low end and the high end set properly. It takes some time and some fiddling with it to get it right. Once it's right, though, all you should have to do is adjust the high end for day to day changes in the atmosphere/weather.

The note of the engine noise should increase slightly then quickly drop back as you pinch the tubing. As I said, this should be a very quick action... the pinch and release.. less than a second for sure..like a quarter of a second

CGr.