Yeah, trust me, if your bike is anything like the Yager GT 200i, you don't want to fill the gear casing all the way up to the fill hole... I did that, and it pulled oil into the air filter box, which dripped out of the little rubber bulb at the bottom back of the air filter box.
I now put in 250 ml, as I think 180 ml is too little. I bought the Mixmizer giant syringe so I can measure the amount put in. Works like a charm. No oil is drawn into the air filter box using 250 ml.
I also went with a thicker oil. I kept seeing metal in my gear oil, so much so that it was glittery. I changed from Lucas 75W-90 to Royal Purple MaxGear With Synerlec 75W-140, and now there's no metal in my gear oil. So if you're seeing the same, that's something to try.