After dinner I swapped the 44 Keyster pilot jets for 42 Keihins, and as a baseline set the pilot screws to about 3.25 turns out.
Hmmm...this is getting pretty close; the light-throttle AFR's are zoning in where I want them.
Hiway cruise AFR on a warm motor was generally in the very high 13's pushing near 14. Ideally, I want that to be slighty above 14.
Warm motor idle hovered about 13. I think the pilot screws can come in a bit without compromising idle quality, and maybe that will be enough to get the hiway cruise AFR where I want it.
The throttle response is excellent. The motor pulls cleanly from 2k up. Needle to main transition is excellent. High RPM WOT is where I want it.
I never would have thought that a needle change from N3RF to NBZT would have necessitated such different pilot circuit tuning. But it did!
Getting the low speed circuits dialed in is basically a matter of balancing the throttle plate bleed hole diameter, pilot jet size, pilot screw settings, and matching it all to the needle.
I plan to pick up an extra set of Keyster 42 pilot jets. I may then custom drill or ream the Keihin 42's to something larger than 42, but smaller than 43. Not sure just yet. I'm gonna run the Keihin 42's as is for awhile & tweak the pilot screws.
