Even with subtracting base resistance most meters are wildly inaccurate measuring below a couple of ohms. A Wheatstone bridge is required to get an accurate measurement, but yours seem "close enough". Unless you get a large difference in readings taken between all three possible measurements between the yellow wires, the stator is likely OK, they are super durable. Same with the field coil.
You can test that the field coil is working fairly easily. Hard way:Take the alternator cover (with coils) off and switch the bike on (don't start it unless you want an oil bath!). With a decent battery you should have a strong magnetic field from the field coil, enough to pull a steel tool strongly against it. Easy way: A smallish wrench should stick and hang on the outside of the cover with key ON.
If no field... check the wiring from the coil to the r/r. The connections under the side cover are very suspect. If all good, check the r/r connections. The field coil polarity is not important but it should get close to battery voltage between its two wires with key ON and a good battery. If the field seems strong, check those connections... the stator wires need to have solid connections all the way to the r/r as well. With OK stator and field coils, good strong magnetic field when ON... the alternator itself has to be working well. The rotor is just a complicated metal lump that bends the magnetic field and, if intact, it has to work. That leaves the rectifier and the battery connection as suspect.
