It is a good thing I took a look see at my old K&B Sportster 20 engines. My memorymust be going bad as I had totally forgotten that these engines had the K&B carb and not a Perry carb on them. I remember now as to why I got them, they were cheap, but the carbs had a dual detent making them perfect for multi-engine planes. usually the excess engine vibrations would cause the spring loaded needles on the Perry carbs to move around on you.

K&B back then like most engine manufacturers was not including a muffler pressure tap. But later they all started doing it. Note the muffler extension has a spot for drilling and tapping to install a pressure fitting.




A Perry carb looks like this one here, this is a later model as the needle has a skirt on it hiding the spring tensioner under it. The spring keeps the needle from moving. But excess vibrations can cause the needle to turn when you don't want it too. But for single engine applications with a balanced prop, it works just fine,




The brass disc is what you turn to adjust the idle mixture on a Perry carb. Just a tiny bit of turning on the disc is all one normally needs, don't try big turn movements, just little tiny incremental adjustments.