1/4 throttle very lean
03-21-2014, 11:15 PM
#1
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1/4 throttle very lean Put a wide band on the car and while in part throttle the car wants to die and goes to 16.1..is this a prob with the air bleeds and is it the high or low bleeds. .I have the power valve blocked and increased primary Jets From 76 To 84..The Secondaries Are Also 84..before and after the power valve block it does the same thing and goes really lean
03-22-2014, 08:49 AM
#5
What RPM does the problem occur at? I assume at cruise/not accelerating?
Also what are the AFR's when you are wide open and at idle? How many turns are the idle mixture screws turned out?
High speed air bleeds and main jets control AFR above maybe 3000 RPM. Idle screws control AFR at idle only. Idle feed restrictor (IFR) and low speed air bleeds are the intermediate circuits and control every thing inbetween these two RPMs.
Your quick fuel should have replaceable IFRs. Think of that as a main jet for the intermediate circuit.
Also what are the AFR's when you are wide open and at idle? How many turns are the idle mixture screws turned out?
High speed air bleeds and main jets control AFR above maybe 3000 RPM. Idle screws control AFR at idle only. Idle feed restrictor (IFR) and low speed air bleeds are the intermediate circuits and control every thing inbetween these two RPMs.
Your quick fuel should have replaceable IFRs. Think of that as a main jet for the intermediate circuit.
03-22-2014, 01:53 PM
#7
I think we're having close to the same issue with our qf850.
mine is stock with the power valve up front. I had to jet the primary from 76 to 80 and the 2ndary from 84 to 88.
now i'm running 12.9-13.2 at wot. I plan to bump both up 1 jet 77&81.
it extremely light throttle i'm running up in the 18.0 area. just past 2-3% throttle the carb pours on the fuel and it cleans up. idle is 13.0 hot. I need to lean up the idle but I just upped the primary jets to richen things up.
anyways, I think were experiencing basically the same thing with the same carb. I need to figure out how to richen up my super light throttle when cruising 20-30mph.
mine is stock with the power valve up front. I had to jet the primary from 76 to 80 and the 2ndary from 84 to 88.
now i'm running 12.9-13.2 at wot. I plan to bump both up 1 jet 77&81.
it extremely light throttle i'm running up in the 18.0 area. just past 2-3% throttle the carb pours on the fuel and it cleans up. idle is 13.0 hot. I need to lean up the idle but I just upped the primary jets to richen things up.
anyways, I think were experiencing basically the same thing with the same carb. I need to figure out how to richen up my super light throttle when cruising 20-30mph.
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03-22-2014, 07:10 PM
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This sounds a bit like when the power valve is not opening early enough, never liked the idea of removing primary p/valve and then jetting up the front.
Maybe speedtigger could have better understanding on this one.
Maybe speedtigger could have better understanding on this one.
03-23-2014, 08:17 AM
#10
Up the IFR a size or two and maybe restrict the idle airbleed one size smaller and see what that does.
I would also drop the main jets two numbers and retune the idle mixture. You are way rich.
I would also drop the main jets two numbers and retune the idle mixture. You are way rich.
03-24-2014, 06:24 AM
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Changed low speed air bleeds from 73 to 68. .that was the only Size I had..Now It Will Cruise And The Car doesn't Wanna die..Afr At 2000 Now Is 10.5. I'll change the low speeds to lean it out..main jets I went from 84 squared to 80 sqaure and afr went from 11.5 to 12.9. I'm getting there
Last edited by 6secNaLs1; 03-24-2014 at 06:25 AM. Reason: spelling