2008 Yamaha YZF-R6 - Scream II

"New from the tires up" is the word from Yamaha about the '08 YZF-R6. Market research showed that R6 owners were happy with their bikes' styling, so an effort was made to update the look and performance "while maintaining the R6 identity."

The new swingarm has stiffening ribs inside the cast rear portion. Thicker material is used in the pivot area, and the axle blocks are now forgings instead of extrusions. An updated Soqi shock still has separate high- and low-speed compression-damping adjustments, but the adjusters themselves are now coaxial instead of separate. The spring is slightly stiffer, and the damping adjusters have more range. The rear Qualifier, like the front, also has a thinner sidewall and revised construction, and the aramid belt is now steel. The subframe is a cast magnesium piece, made possible by further development of Yamaha's controlled-fill die-casting process, and saves one pound.

The updated frame is stiffer in the steering-head and engine-mount areas with thicker material, but thinner rails (by 0.5mm) and the removal of the small cross brace behind the steering head slightly reduce overall rigidity. The more flexible frame is intended to work with the stiffer fork to improve front-end feel and the stiffer swingarm to improve traction and feedback under acceleration.

While the front end may look identical to the previous version's, there are plenty of changes. The brake discs are now 5mm thick (up from 4.5mm) for better heat dissipation. A new variant of Dunlop's Qualifier has a thinner sidewall and altered construction from the previous version to improve steering response. The bottom triple clamp grows in height from 35mm to 40mm for more rigidity, the fork springs are slightly stiffer and the damping clickers all have a wider range of adjustment.

The riding position has been rotated forward and down slightly, with the seat 5mm forward and the clip-ons 5mm forward and 5mm lower than previously to put more weight on the front end. The outer fork tubes are stiffer and 10mm longer to allow for a greater range of ride-height adjustments; likewise, the rear end can be dropped 7mm farther than before to accommodate large-diameter race tires. The gauge package is unchanged for 2008 aside from the background color.

A slightly more convex piston crown increases compression from 12.8:1 to 13.1:1. The titanium valves and camshaft profiles are all unchanged, but the exhaust timing has been advanced by one degree. New valve springs are made from an improved alloy but have the same rate as before, the connecting rod bearings are 1mm wider and made from a different material, and the main bearings are also a different material and have an increased oil supply. In all, more than 50 detail changes inside the engine were made to reduce friction. While the ramp-style slipper clutch is identical to the previous version, engine braking has been reduced by using the YCC-T to hold the throttle butterflies open slightly on deceleration.

The highlight of the engine updates is the addition of the Yamaha Chip Controlled Intake to the 41mm throttle bodies, which retain the ride-by-wire Yamaha Chip Controlled Throttle first introduced on the '06 model. The YCC-I is similar to the setup used on the '07 R1; at low rpm and small throttle openings, the intake extensions are in the lower position for a total funnel length of 66mm to optimize midrange acceleration. At 13,700 rpm and more than 60 degrees of throttle opening the extensions lift away, leaving the short, 26mm funnels to optimize top-end power. Last year's funnels were 31mm tall. A new airbox and relocated filter maximize ram-air efficiency; on the other end the crossover tube in the exhaust is larger and the muffler cap more compact.