600ml is the norm , but as joe said fill it until you can see it full at the dip/plug hole i have had some luck just draining the tank and a fill to top with fresh and allow to sit a couple of days soaks it out sometimes then get it to fire and it sucks the bad out and in with the good ..
or it can get to be some fun cleaning jets n stuff out , at worst if you cant find it a different air cleaner will fit on there just be sure it doesnt foul any linkages
