My experience is that an excessive amount of oil coming out the breather is due to an excessive amount of "blow-by" from the piston. You may need to refresh the top end.
I have been putting the recommended amount of oil in the tranny and in the engine. I do not fill it up to the max each time I do an oil change.
How do I know if I need a new top end on it. I got the bike last November and I ride about every 2 weeks when I get a chance. It still runs strong and starts up in about 2 kicks.
How many hours are on the engine? I'll venture a guess it is unknown. Picking up an hour meter and a Factory Honda Service Manual will be two of the best purchases you ever make.
Just because it says 800ml (or whatever it says) on the sidecover does not mean to put that much in after a change. The stated capacity is probably if the thing is bone dry for initial assembly, and you never get ALL the oil of there when draining it.
Unknown engine condition would indicate perhaps you should check your compression and plan on spenging a bit more than a piston and ring kit to get it back to a level you can feel won't end in a pile of tears and metal fragments.