1 hour ago, v-twinwalker said:
Google is your friend.
Mikuni, Kiehin ... same idea!
For Keihin Carbs the jet sizes refer to the metering orifice (or flow rate) diameter, expressed in millimeters. A # 100 jet is 1.00mm in diiameter. A # 38 Jet is 0.38 mm in diameter. A #35 jet is 0.35mm in diameter.
The smaller the jet size, the less fuel will flow through it at a given pressure difference across the orifice boundary.