Finally got my replacement stock BST40 needle today. Wow, I had to move it from clip 2.5 to clip 4 to get similar AFR readings. My old needle was very worn, both in a central area and also near the tip. I have gone up 7.5 on the main so far but I'm still testing it out.
Since I ran through a few clip positions today I was able to see a bit more about the strange AFR readings. It seems pretty stable when I keep the mixture towards the rich side, and at certain rpms it is not very tolerant of a lean-ish mixture. Seems that once it gets to a certain lean-ness it begins to falter more, so it looks like I may just need to avoid going lean when it is on the cam.
I think from the first day I put in the G1 cam it has acted a bit more finicky regarding jetting. My first ride with the G1, and with stock cam appropriate jetting was filled with pops and bogs. I'll have to go dig up my notes to see what I did as a jetting correction. So far I've just been running the same AFR across the whole throttle.
This weekend I've been setting it up for a stable AFR in a richer zone. I should be pretty close. My last ride was with #4 and a 160 main and it was just about where I want the AFR to read. I've upped another 1/2 clip and gone to 162.5 main for tomorrow's ride.
My last mileage check yielded only 40mpg.