Cycle News

2015 YAMAHA YZF-R1 AND YZF-R1M FIRST RIDE P48 T H E H A R D W A R E >>THE ENGINE Yamaha YZF-R1 Project Leader Hideki Fujiwara said it best to me at SMP: "Development never stops, but for this R1 it had to be the best around a racetrack. The engine must be fast, the chassis must be light." Sounds simple, really. In reality, it's not. For the 2015 YZF-R1, Yamaha started with a clean sheet of paper. Still the crossplane engine for- mat was retained, however all the internals were rede- signed or lightened as well as extensive use of mag- nesium for the cam, clutch and side engine covers, as well as the sump, to create a powerplant that's a massive 8.8 pounds lighter than before. The new engine still displaces 998cc, although bore and stroke was changed to 79 x 50.9mm for higher rpm performance and com- pression has been raised 0.3 to 13.0:1. Reducing inertia and internal mass was critical in helping to attain the faster rev speeds of the engine, which is now 1.3 inches narrower at the crank axis area. The air intake was repositioned and now sits at the very front of the machine through the steer- ing pipe, just like Vale's M1 to pressurize a 24 percent larger airbox. Fujiwara again: "With this new en- gine we needed to greatly increase the air intake flow and pressure, so we looked to the M1 MotoGP bike. The intake is now in the highest pressure area, and this greatly helps high rpm performance." Regarding the YCC-I (Yamaha Chip Controlled Intake), the high rpm fun- nel length is 20 percent shorter than on the previ- ous R1 to flow more air, quicker. This works with a repositioned primary fuel injector that's angled straighter than before. Yamaha found the old in- jector was spraying fuel at too flat an angle, reducing atomization and ultimate performance. The new angle ensures fuel lands on the back of the intake valve, ensuring a cleaner, more powerful burn. The 2mm larger intake (30mm) and 1.5mm larger (26.5mm) exhaust valves, actuated by lightweight rocker arms that look sus- piciously like those off the BMW S 1000 RR (not the old cam over bucket sys- tem), sit in a redesigned combustion chamber that's machine finished rather than cast to reduce the variance in compres- sion ratio across the four cylinders. New camshafts have 0.6mm more intake and 0.2mm exhaust lift, while also having reduced valve spring rate, again, all for less drag and more power. The Yamaha Chip Controlled Throttle (YCC-T) has four different settings and houses 45mm throttle bodies. The 4-2-1 exhaust is a titanium job and is assisted by a new EXUP valve that's closed below 7500 rpm and open above it to ensure more greater exhaust gas evacuation at high rpm. Into the guts of the engine now and the three- ring pistons are a MotoGP- style bridge-box design that's 8.5g lighter even though the bore size has increased by 1mm. These are attached to titanium, fracture split connecting rods, which is a world first on a production motorcy- cle and 40 percent lighter than a steel rod. The cylinders them- selves are offset 2mm to the exhaust side to help reduce the force of com- bustion moving the piston against the cylinder wall. Less friction, more power. Talking about less friction and inertia, the narrower crank's inertia has been reduced by 20 percent as the bal- ancer weights have been positioned on the outside of the first and fourth cylinders. Crank cooling is done by separate oil paths that supply the big-ends and rods. A new air-cooled oil cooler has been used as Yamaha believes this makes oil temps more stable in race conditions by flowing a greater vol- ume of air than they could coolant. Moving to the quick- shifter-equipped gearbox and gears one to four have all been reduced for better roll on acceleration. The cam-type slipper clutch has also been redesigned and is 19 percent lighter and seven percent smaller in diameter and is excep- tionally light at the lever. >>THE CHASSIS Targeting the feel once again of the M1 MotoGP bike, the new twin-spar chassis is much more rigid for track riding. Over the course of its development, Yamaha engineers would start testing components on standard DOT tires and eventually finish on slicks, so they could be sure the bike would be rigid under track and race conditions. The engine is mounted at the cylinder head and the crankcases—Yamaha engineers noted on some examples of the previous R1 the frame spars would blow out under heavy brak- ing, so they fitted a cross member running across the top of the spars to counter this problem. The increased rigidity is aimed primarily at better front-end feel under brakes and on initial tip-in. A magnesium subframe sits at the back of the bike. The 15mm shorter swingarm is an upward truss type unit that has been utilized and helps to give a wheelbase that's 10mm shorter than the pre- vious R1. The upper truss style was used partly for corner entry stability but also for room for the new KYB shock to be fitted continued on page 52

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