Stock Aisan 4K Carby Leans Out

[luk3333]

After installing my AFR I've noticed that the carb leans out really bad when you jump on the throttle (like to 21 AFR). I previously thought it was bogging down to over fuelling but obviously not. If i put the choke on about 1/4 it solves the problem but idles rich, usually it idles stoich right on 14.7. So I'm thinking it might be a partially blocked jet in the secondary throat? I'm not very experienced with carbs so some input would be great.

[altezzaclub]

check the pump diaphram is working- just look down the throat and work the throttle by hand. You should see a stream of petrol squirted in down by the venturi.

 

It is meant to richen it when you boot it, so if that is where it is lean I reckon its blocked or leaking.

[luk3333]

I've seen it do that before when I've been tinkering before this issue, I'll have a look, cheers

[luk3333]

Yea, the valve was stuck, all fixed, cheers :)

[luk3333]

So its not quite fixed, its better since i unstuck the arm that controls the pump, but if i put my foot down suddenly at any rpm i can see it go up to 16 on the afr then slowly drop back to 13 or 12 and i can feel the power come on. It's not that bad when highway or town driving, but it kills spirited wet driving. I can see the pump diaphram squirting in extra fuel when you apply throttle and i can't detect this problem when idling but when in any gear if I boot it, it just leans out, accelerates slow then picks back up as it richens up again

[altezzaclub]

What's the second choke setup? Still vacuum?? Any chance of the second throat opening before the intake velocity is built up enough to cover it?

 

It sounds like a full carb strip into a thousand pieces and go over it with solvent and a compressor. The Celica was leaning out like that on the rally two weeks ago so I pulled the DCOEs off and did exactly that. Steve said it pulled like a schoolboy all night over this last weekend. Must have been some dirt in the drillways or something in the jets I couldn't see.