Couple of Carburetor Questions

Hi all, I finished my 49cc install, having a ball with my bike but need advice

Im at 5700 feet altitude and think Im gonna have to do some jet work so I have a couple questions;

---when I replace the main jet (I'm going smaller) do I have to replace the needle too?

---how much of a gap should the slide in the carburetor have at closed throttle (idle)?

Thanks all for the help

1) You wont have to "replace" the needle, just adjust up or down probably......


2) I dont believe there is a standard measurement, whatever it takes to feed enough air to the fuel for idle.....

I always set the idle up by turning the screw out until it sounds like it's idling I.E maybe only slightly higher than the amount needed to keep the engine running.

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