Breather system

I have a similar breather, almost like yours. But I have added a rubber duckbill valve at the end of the hose to prevent it to inhale water and dirt in deep water crossings.
Different oils are giving different oil dribble from the breather tube.

Maybe have you started using another type/brand of oil?
For me it is: Mineral oil - dribble. Synthetic oil - little dribble. Mobil 1 - no dribble at all.

If you get more blowby from worn piston/cylinder or even a holed or cracked piston, you will get a higher flow through the tube and that will carry more oil with it.
Or are you just gassing it more?

One advantage of rerouting the breather like we have done is that the oil dribble will not end up in the carburator, where it might cause trouble.

Regards.

What a duckbill valve looks like:

what is the need for this breating system. i disabled the system. what is function of it ?

first of all, put your year and model bike so we can tell what you're talking about. all internal combustion engines need to vent. if you don't use the factory setup, cap the frame and route a hose anywhere you like keeping in mind an oil mist will be coming out of it.