Hello All,
Like most of you our bikes run cold under 75F ambient. In winter i get 4-5 mpg less than summer time. So experimented around last winter with blocking off the radiator as the t-stat checked out good and 3 yamaha dealers blew me off. A 4.5in tall plate does the trick to get the bike up to the 175F mark for the better mpg. Bike has 89K miles, ridden daily on the freeways splitting lanes in Southern California.
I split some vacuum tubing and glued it around the metal plate and added some foam tape to the back to protect the radiator and hold it in place with HD zipties.
Hope this helps anybody that is interested.