I have two Yamahas and I have noticed that the shifters are sloppy no matter how you tighten them. This is what I did to resolve the issue. I removed the shifter and drilled a hole with a 9/64 drill bit on the bottom side. I placed the hole not dead center but a little towards the outside edge of the shifter. I then used a 8-32 (29D) tap on the shifter. I then placed a 8-32 set screw in the shifter, just enough to start the threads. I now installed the shifter and tightened the mounting bolt. I then tightened the set screw. I used a little locktight on the set screws. I did both bikes and this modification was well worth it. I can feel neutral and each gear much better now.