The 41 custom drilled/reamed pilot jet experiment is a success. I did this in two steps; first step, .4mm drill bit(in pin vice); second step, .41mm (actually .016") reamer (also in pin vice); this brought the Keyster 40 to a custom 41.
At this point, at a very relaxed pace I can swap out pilot jets in less than 40 minutes, start to finish. It took a bit longer this time in order to drill and ream the pilot jets, though.
In wild anticipation of a test ride I forgot to scribe the pilot jets as being modified...oh well, maybe next time, if I ever need to remove them.
I went with 3.75 turns out on the pilot mixture screws as a starting point/baseline. As a general rule, a 1 step size change (single digit change, in my case, from 42 to 41) will require a .75 turn change on the pilot mixture screw to maintain comparable idle AFR's all other things equal.
Initial test weather was clear & dry, temps in the low 60's, low humidity, & gusting winds. On a fully warmed motor it idles in the low to mid 12's; flat, light throttle highway cruise is now in the low 14's.
This combination is better, and should reclaim some cruise economy. I really want the cruise AFR's to be in the low to mid 14's. I think the pilot screws can come in just a bit, maybe an eigth of a turn, maybe a little more.
When I'm happy with the pilot settings, I'm going to concentrate on vaccum piston (slide) transfer port size and G-pop baffle angle (exhaust)...
