[rusaccord]

I'd say that that is a chopped 600RR exhaust on that chop. Also, is Yamaha going to have to go to the same multi-link style suspension that Honda put on the 600RR and the 1000RR to do a direct-route undertail exhaust? I know that this is already in place on the R1, but I haven't had a chance to take a look at them. If yes, then that pic is way off, since it is still using the standard rear suspension form the R6.

 

[rusaccord]

I'm guessing that aerodynamics more than anything else. I'm not sure how much drag there is from a traditional exhaust. But I'm thinking that the undertail does not eliminate nearly enough drag to justify itself and its high cost. People probably just thiunk itlooks cool. That, and stupid passengers will stop burning their legs.

The biggest plus for the manufacturers is that they capture a whole new product market by putting an undertail on - this separates the bike with the undertail from the previous bikes with the traditional exhaust. It magnifies the feeling that the bike is part of a "new generation" and thus more appealing to squids the world over.