Pretty sure it has two needles, there just appears to be only one knob….The white outer knob is for high speed, initial setting is 3/4 turns out from gently seated…You will disconnect the linkage off the needle before resetting the needle though. The red knob is for low speed, its initial setting is 1.5 turns out from gently seated. Again, you will have to disconnect the linkage from the needle before resetting it…
Is the needle actually spinning on its own, or is the linkage just spinning on the needle? If the needle is actually loose and spinning freely, it can be tightened by snugging up the brass packing nut surrounding the needle on the carb…