How does the needle/clip work?

[mr pibbs]

I understand that the clip position can affect midrange bogging, but how does it work? What exactly am I changing with the change in clip selection?

[Bear45-70]

By partially blocking the fuel outlet into the venturi (on some carbs the needle actually sticks into the main jet itself), thereby lessening the amount of fuel entering the engine. The taper of the needle and how far down it sticks varies that mixture. The clip lets you change the fuel map as the EFI guys would say, by moveing the starting position of the needle up and down.

[mopar4u]

By partially blocking the fuel outlet into the venturi (on some carbs the needle actually sticks into the main jet itself), thereby lessening the amount of fuel entering the engine. The taper of the needle and how far down it sticks varies that mixture. The clip lets you change the fuel map as the EFI guys would say, by moveing the starting position of the needle up and down.

yup, your making your air fuel mixture leaner or richer depending on which way you move it.

[hondaman]

Moving the clip down on the needle will give you a richer mixture.
Moving it up will lean out your mixture.

[Lunytune]

So after installing a big bore kit, which way should the clip be moved? Up or down? I have a 6mm overbore on an AF05 and a 50mm kit on an AF16, and soon to have a 44mm kit on an SB50.

[mookie]

big bore need more wampum.

[Bear45-70]

So after installing a big bore kit, which way should the clip be moved? Up or down? I have a 6mm overbore on an AF05 and a 50mm kit on an AF16, and soon to have a 44mm kit on an SB50.

You want to move the clip down on the needle. This raise the needle making your mixture richer.

[mr pibbs]

Got it. So if i set the clip lower/needle higher, i will engage the main jet sooner?

I went ahead and set mine richer for break-in

[Bear45-70]

Got it. So if i set the clip lower/needle higher, i will engage the main jet sooner?

I went ahead and set mine richer for break-in

Be advised that the needle will NOT enrichen the mixture at WOT, it only adjust affects midrange. Only the main jet controls fuel flow at WOT.

[Wheelman-111]

Greetings:

I think it's important to get across that just moving the needle clip isn't sufficient after a big-bore installation. The main jet needs to be replaced with a larger one, period. The clip may be adjusted for fine-tuning the midrange once the engine's needs are determined, but you can't rely on a richer needle position alone to prevent meltdown.

There are people who appear to be able to distinguish too-rich from too-lean at the twist of a throttle. There are many more who profess to have that ability. I'm certainly not one of them. After 3 BBK installations on 3 engines, I can sort of tell, but my correct prediction ratio isn't much better than flipping a coin.

I strongly recommend that a reliable temperature gauge should accompany any big-bore installation, carb or pipe upgrade. Frequent plug reads are a poor second option, unless you know what you're looking at, and obviously start rich from ideal. The bore you save may be your own.