DBM, if your reading - When you tuned your PWK38, you mentioned needing needle "N427-48-
EEN/017-455". I'm thinking I might need this needle too. When I'm on the JetsRUs page for the N427-48, they don't list the EEN/017-455. They have an EEM/017-454. Link below.
The needle in my carb is totally unmarked, so I don't even know what my baseline starting point is. According the the Keihin carb parts page, the standard stock jets are 170, 55 and Needle 48-DDJ for the PWK38 Air Striker. Since my carb came with the 170 and 55, it might be reasonable to assume the needle is a 48-DDJ. (You thought the needle that came with your carb might be an ECN.)
I'm struggling to make sense of all the tables and charts on the JetsRUs page. Codified alpha-numeric soup. Was your decision for the EEN based on "more taper, but longer and larger diameter" for a leaner more progressive needle and then use the 4th clip groove to adjust it richer.
Where I'm at right now (before testing the 125 main), it feels like the fuel mixture is about right in the low midrange and then goes rich in the upper midrange with the e-clip in the middle groove.
I'm trying to think through what taper, length, and diameter relative to the 48-DDJ would correct it.
Heck, maybe I just need a better flowing air filter setup and this stock setup with the air box cover removed just isn't cutting it. But I stubbornly believe I should be able to make it work better.
https://www.jetsrus.com/a_jets_by_carburetor_type/needle_keihin_N427-48.html