2008 Yamaha YZF-R6
Yamaha made more than 50 engine changes for '08 to improve the high-revving R6's power and durability. Direct-plated ceramic-composite cylinder bores dissipate more heat and reduce frictional losses, as do wider connecting-rod bearings and new crank-journal bearings with increased oil flow. A more convex piston dome boosts compression from 12.8:1 to 13.1:1. The Mikuni EFI system has had its mapping revised to improve cylinder filling and features a quartet of 41mm throttle bodies. A primary injector located below the butterfly is paired to a showerhead-type secondary injector, activated at 6000 rpm. Directignition coils, dual-electrode sparkplugs and a high-output magneto deliver accurate, reliable firing, and combustion byproducts are evacuated through a stainless steel header and gP-style under-engine muffler containing triple exhaust catalyzers and an O2 sensor. A titanium EXUP exhaust valve located upstream from the muffler broadens the powerband by managing exhaust pressure resonances, and a titanium silencer trims a bit more weight.
Fly-by-wire throttle activation-aka YCC-T-provides seamless response on the '08 R6. A conventional push-pull cable operates an Accelerator Position Sensor located on the throttle body bank,which communicates via the ECU with a Throttle Valve Drive Motor that electronically controls the butterflies for optimal response under any riding condition. New to the R6 this year are the YCC-I variable-length intake funnels that debuted on the R1 last year. The intake funnels measure 66mm in the tall position (35mm taller than last year's fixed 31mm funnels), substantially boosting torque production and enhancing low- and midrange power. When the motor reaches 13,700 rpm (with over 60 degrees of throttle opening) an electronic motor instantaneously snaps the funnels to the short length of 26mm (5mm shorter than last year) for more responsive high-rpm acceleration.
The R6 Deltabox aluminum frame is new for '08, combining a thicker cast headstock and stiffer cast motor and swingarm mounts with new spars made from pressed-aluminum plate to shave weight and optimize rigidity. Yamaha reports that vertical rigidity has been reduced by 4.6 percent and torsional rigidity by 2 percent-changes that, along with a deleted crossmember, improve front-end feedback and handling response. A die-cast magnesium subframe-a first for Yamaha-shaves 1 pound from high up on the chassis, improving mass centralization and lessening turning inertia. A new swingarm has likewise been tuned for optimal rigidity, with internal ribbing added to a thicker cast pivot section (that mounts higher on the frame for increased anti-squat effect) and spars that are now forged instead of extruded. These changes result in a claimed 11 percent increase in vertical stiffness and a 9.1 percent increase in torsional rigidity, to improve traction for better acceleration out of corners.
Suspension is four-way adjustable front and rear, with high- and low-speed compression damping at both ends, setting the R6 apart from its classmates. The 41mm inverted fork is now held by a wider lower triple clamp to increase torsional rigidity and front-end feedback, while the outer legs have been extended 10mm to allow greater ride-height adjustability. Stiffer fork springs (9.0 kg/mm, up from 8.8) better resist hard braking, and the shock spring is also firmer (10.5 kg/mm, up from 10.0) to balance the stiffer front springs. A 7mm ride-height adjuster has been added to the shock as well to increase chassis adjustability and accommodate the use of taller, race-profile tires. Radial-mount four-piston front brake calipers are unchanged save for slightly thicker rotors (5mm, up from 4.5mm) for improved heat dissipation.