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Carb pump jet operation


NickJ

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So I have a pair of Dellorto drla downdrafts on my Lada, i've been chasing a flat spot coming off idle for a while, increasing the idle jets has improved it slightly but i'm now on jets that are way big compared to the suggested start point, added to that open road fuel consumption is not as good as it should be so my gut feeling says rich as.

Onto the point of the thread, when the pump jet first flows its at about 1/3 stroke, should it flow right from first opening or once the progression holes have done their thing? i've adjusted the pumps to full stroke and it improves but will take some fiddling to get pump flow any earlier, can anyone confirm the start point for me?

Hope to borrow a wideband next week to sort overall jetting next week before Hamner, would like to have the pump jets working right so I don't have to worry too much about that circuit.

Cheers!

Specs

drla 36
30mm venturi

122 main

55 idle (may be +/-1)

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idiot post....

Well I can now confirm the pumps operate from 0, pulled the diaphragms out to check they were correct and found I hadn't replaced the springs when I rebuilt them last year, with the springs in the flat spots gone and she gets off idle much nicer.


 

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