Yup, that's the needle jet.
You might be able to clean things up with ultrasonic? Be careful cleaning brass parts such as the needle jet, and especially the needle which slides up and down inside that jet. Any vigorous cleaning will remove metal, which will affect the fuel metering function of the carbs. So better to rely on solvents, ultrasonic or wiping with a cloth. Best to avoid emery or metal brushing of the brass parts.
Or buy a kit, but make sure you get the right parts in the kit. Different sizes of main jet, pilot jet, needle size and needle position are the main ways of tuning the mixture on these engines.
Might be that somebody has put antifreeze in the bike, maybe to protect the tank from rust? But modern fuels go gummy and green when left for a long time.
Looks like progress!