I also had slight headshake on decel from 50-40 on the new Michelin Road 5. Not sure about these tires yet (only about 100 mi in). I usually use PR4GT and those would only shake after they were about half worn. So I thought it was the new tire. Had it rebalanced to zero on the machine. Long story short, the bike has 15k miles and was due for bearing regreasing/torque. I did this myself. Took everything apart and the both top and bottom bearing was still greased well and no visible wear. Replaced grease, put everything back together and went for a ride. Headshake was noticeably less but still there. So I decided to install All Balls tapered bearings and wow, what a difference in feel. The bike feels like new, solid, planted, and no more headshake. The biggest improvement is the reduced vibration at all speeds. The bar buzz is like not there compared to before. This is a must have upgrade people!
Yamaha, please stop putting cheap bearings in your bikes that you increase MSRP on every year.