It sounds like you're delving into some serious tinkering with your engine! Regarding the mysterious nipple in the second picture, it might serve as an overflow or breather for the carburetor. Typically, it's left open to the atmosphere, but
spectrum billing support it's wise to double-check your carburetor's manual or reach out to Zongshen for confirmation. Better safe than sorry when it comes to engine components! If you're uncertain, covering it temporarily while you gather more information could be a cautious approach.