Carb Acc pump spring arm question???

[StuHERTS]

Attached pic to explain ,
but what affect would this have if it were to be screwed too far in/out with what effect on AFR's?
I just wanna get to grips with AFR richness/leanness and how to compensate.

1.2 main
1.2 2nd
1.25 ac

[casper]

Everytime you get on the throttle the acc jet squirts fuel to richen things up.The arm controls how much ot squorts.Afrs always richen up sometimes flat 10s when you get on the throttle but should only be for a second.I think a longer throw on the arm is more fuel.

[JP Racing]

It's been a while now but from memory I used to set the accelerator arm up so it was fully open when you could fit a 5mm drill bit into the throttle butterfly as this seemed to give a good all round performance.

If you had it shorter it could chuck too much fuel in early on causing a flat spot on light throttle as it squirts to much fuel in.

The same can happen if you go the other way if you have it so the throttle butterfly is open too much it could lean off the fuel mixture too much on part throttle.

Hope that helps

[mingblus3]

It's been a while now but from memory I used to set the accelerator arm up so it was fully open when you could fit a 5mm drill bit into the throttle butterfly as this seemed to give a good all round performance.

If you had it shorter it could chuck too much fuel in early on causing a flat spot on light throttle as it squirts to much fuel in.

The same can happen if you go the other way if you have it so the throttle butterfly is open too much it could lean off the fuel mixture too much on part throttle.

Hope that helps

This sounds like the problem I am experiencing I have a flat spot on light throttle. How do you sort this out. Confused about the 5mm drill bit.

[Wallace]

https://www.rtoc.org/boards/showthread.php?t=27381

Bottom left hand picture of this article should stear u in the right direction

Setting this correctly has seen the biggest improvement in the fuelling of my car

Any probs give us a shout, as at first my dumb ass brain couldn't grasp it

[JP Racing]

To start off with pull the throttle a few times whilst looking at the accelarator pump arm you should notice when it gets so far the arm stops moving and it pushes the bar through and it compresses a spring. Once the arm is fully open you should try and put a 5mm drill bit in between the open throttle butterfly and the body of the carb to see how far the throttle is open a 5mm drill bit should fit snugly in between.


If it needs adjusting you hold the carb in your hands with a 5mm drill bit at the ready and open the throttle up and place the 5mm drill bit in between the side of the carb body and the butterfly holding the throttle open. Now you have to adjust the accelerator pump arm until it is fully open at that point so as you open the throttle more the accelerator pump won't put any more fuel in as the accelerator arm is compressed as much as it goes

Hope that makes sense :/ I can put some pictures up tomorrow if needed but don't have a carb here at the moment

[StuHERTS]

Thanks Guys,
yea i believe i set the butterfly with a 5mm drill bit but as you suggested earlier, it still seems to throw too much fuel in when i first touch throttle and i do get AFR's of 10 which actually hold for about 2-3 secs then goes up to 11.3-12 @ wot (running a bit rich as ive dropped boost to 1bar until ive rectified this).

I "think" i need to reduce the length of play the arm has as to reduce squirt amount?.

I thought the arm just squirts fuel in to the well via the diaphragm, or does it do both?

Not the best of vids and hope you dont feel sick watching it but you can see the AFR sticks on 10 for a little too long.

http://www.youtube.com/watch?v=oiqbqP12gqw