[VFR750]

Paul,

OK, this sounds good. I was conscious during the initial rigging to have the 1st port covered at idle. But thinking about the need for more air at idle with the bigger engine makes me wonder if I should make sure the 1st port is covered. I'll think about my idle set up and use the idle air screws. I like the idea of drilling a small hole if needed to keep the 1st port covered.

Originally I had 60 idle jets, and they were too big. I'm currently running 55s although the car seemed a little snappier with the 57 idle jets. With the 55 idles, I'm at ~13 at idle, drop to 11.7-12 under light throttle, but see a slight pause on tip-in. At a steady cruise, 3000 rpm, I'm stuck at ~12, and can't seem to get a better light throttle cruise ARF. Going smaller than 55 Idles seems to be the wrong thing for throttle response. (I'll likely go back to the 57s.)

I was thinking, prior to your comments, about increasing the Idle Air Correction bleeds (jets) from 140, to lean the cruise AFR a little. But you've go me thinking about being a little more conscious of the tip-in behavior...... I may need an idle bleed port kit, but first I need to do more work.


I agree the 165 mains seem too large. At the low end they are way too rich, but lean out by 4500-5000 rpm. I'm pretty sure the main circuit would work better with a smaller venturi and the vacuum at the throat was larger (like the 27.5mm vents in the 2.2)

If I can get a stronger signal, i.e., change the relationship between air flow and fuel flow (forces me to a smaller venturi or even smaller air correction jet) or add more air at the low end (emulsion tube holes) I can hopefully lean out the 3000-4500 range relative to the high end. I'm leaning towards the emulsion tube change, because the WOT 3000-4500 range is too rich.

BTW, we kind of hijacked this thread, everyone OK with that? I'll probably start a Zenith AFR post with charts and stuff as I do more runs.