Bonneville America Forums Forums Technical Forums Performance Mods ARK done now on to AI removal

With stock pilot you will be lean at idle to about 1/4 throttle more or less. The needle meters the fuel from the main and the shim raises the needle changing the throttle position that any certain point of the needle taper is in play. The higher the needle is raised the smaller it's diameter allowing more fuel until you are running off the size of the main nearing full throttle. Different needles have different tapers changing the amount of fuel metered at any given point. Shims are normally used to fix a mid range flat spot if you find you have one but watch as all these come into play in combination at any given point making the mix richer or leaner. I would start with what the calculator suggests with a 45 pilot and the suggested main and tweek it from there. While tweeking the mix make one change at a time and test to determine if that worked or not. If you make multiple changes at the same time you won't be sure what one was good and what one was bad.