Seriously though, i'd start with an oil change, it maybe that you are experiencing false neutrals, had that many moons ago on Suzuki's and an oild change cured. Possibly selector forks worn, possibly gear change lever pivot, could be not firm enough slection of gear, try adjusting the lever so you get a more positive selection. Check this thread for things to look at, same engine etc http://www.svrider.com/forum/showthread.php?t=54588