On the 250, there is a hard vacuum line that goes to the electric choke on the YFA carb. Where does it originate on the manifold? I just replaced the YFA on my '75 and when I moved the line gently so it would clear the carb, it snapped off at the manifold due to corrosion. I can't find where it originated to save my life. The replacement carb doesn't require the vacuum line so I want to seal the hole at the manifold but finding the origin spot has me perplexed. Anyone??
Do you have a picture? If it is the line covered in cloth, that is from the exhaust manifold and brings heated air up to the choke spring to open the choke plate. If your new carb uses an electric choke, you can leave out this line completely as it is not a vacuum line - just heated air.
Yup.... Originally there would have been a fresh air connection on carb or sometimes bottom of air cleaner. That connects to a chamber in exhaust manifold that heats air. A second insulated line connects from manifold to carb's choke port. Vacuum is created within carb to pull the air through the lines for heating. As already stated, if not needed on new carb, ditch the lines & forget about them.
....and don't worry about where it broke off the exhaust manifold. It was just for heat to rise. Nothing is leaking.