Compare the new needle to the old one. The needle needs to be the same length. If it stops, and still too rich, the needle is too short. These tend to vary, especially on the last run OS made of these. I have seen all sorts of stuff. It is supposed to be the same needle from FP.20 through LA.46. Measure and compare everything for anything bent or distorted from the impact. This is a good time to mention OS needles are not the same as Enya, either. These things can have varying tapers on them also. I have taken OEM OS needles and filed steeper, more sharp points of them in order to get a better adjustment. Sometimes the needles are not installed in the knurled hub properly either. Look over noth complete needle valve assemblies for any differences.
Type at you later,
Dan McEntee