I've posed this question to our resident carb expert as well, but in meantime, I'm wondering if anyone knows if there's a difference between the actual needles for PD41B carbs versus the 064A.
Reason I ask is this: I've got '77 CB750F with the PD41B's. Thought I had adjustable '77 needles in it, but going through the file of receipts etc from PO and I see one for NOS needles for '75-'76 CB750F. Looking at the master carb listing here on the site, looks like those needles belong to the 064A carbs.
Since I've been having continual struggles with an extremely lean condition while riding (not while idling) and have raised the needles as far as they go and keep putting larger main jets in, I'm thinking that perhaps the 064A needles are a bit fatter or something? I can see this being the cause of my lean condition if that were the case.
I don't have any needles to compare to, and I can't find any literature giving those kind of specifics for the needles.
Obviously I'll go through the process of finding proper needles, but while I wait for that to happen, it would be good to have some kind of confirmation that this could be the cause.
Thanks.