"clunky" shifting
 

My 'bird seems to be getting clunky to shift and hard to reengauge 1st gear at a stop. The clutch seems fine no drag and no creep at a stop and engauges normally.I use Honda oil and the bike has 15,000 on the clock. My 1000f uses the same oil and shifts smoothly (for a Honda) but is noticeably smoother than the Bird. Any thoughts? A different oil or additive perhaps?
Thanks for any input, Fred