R1 Revolution!

Yamaha’s all-new Superbike for the street.

December 2006

The new 2007 R1 has arrived, to go on sale in December. Read all about it in next month's seven-page cover story, but meanwhile here's a web overview. This bike has two electronic features that the company calls YCC-I and YCC-T. These are, respectively, a variable-length intake system to boost foot-pounds at both the torque and horsepower peaks, and the 1000cc version of the throttle-by-wire seen last year on the 600. What do the letters mean? Yamaha Chip Controlled Intake and Yamaha Chip Controlled Throttle.

The new engine produces a claimed 178 crankshaft horsepower—up 5 from last year—at the same 12,500 rpm. Bore and stroke remain unchanged at 77 x 53.6mm.

Now the BIG NEWS!!! Yamaha gave this new R1 four valves per cylinder, replacing the old version's five valves. The official reason is that this eases meeting emissions (the bike has two in-series cat-cons and an oxygen sensor to meet '08 regs), but emissions are not the reason why Yamaha's MotoGP M1 has had four valves for two-and-a-half seasons. With the new four-valve chamber, compression ratio is up to 12.7:1 and torque is said to have fattened nicely in the midrange. In the past, R1 torque has peaked up above 10,000 rpm, giving a narrower powerband than the competition, whose torque generally peaks at 8500 revs. Five valves have been a Yamaha signature feature for 20 years but if the compromises are easier to untangle with four valves, what's an engineer to do?

Part of the reason for fattened torque is more compression and the new (and, I suspect, faster-burning) combustion chamber, but also on the job is the variable intake system. An intake extension is moved between two positions by parallelogram arms so that the longer intake length boosts torque (probably by about 10 percent) at peak-torque rpm, and the shorter length (with the extensions pulled clear) boosts at peak power revs of 12,500. The redline rpm is 13,750.

This engine has twin 31mm titanium intake valves and paired 25mm (unchanged) stainless exhausts. Last year's fractured-cap carburized steel connecting-rods have been slightly beefed where the shank flares into the big-end.

Last year, only the limited-edition model with Öhlins suspension had the slipper clutch. This year the LE and Ohlins are gone, but all R1s get the non-adjustable slipper clutch. This device, sometimes called a BTL (Back-Torque Limiting) clutch, prevents engine braking from dragging or hopping the rear tire when the throttle is closed from higher revs—especially when entering corners. When the rear wheel drives the engine, sets of 45-degree ramps wedge apart, tending to lift the clutch's pressure plate. Students of (motorcycling) history will recall that the two-stroke era in 500cc GP racing was ushered in partly as a result of MV Agusta's inability to deal with this problem of engine-braking's effects during corner entry. MV's musical megaphone screamers had competitive power, but handling problems such as the above gave the advantage to the two-strokes (which had almost zero engine-braking). Now slipper clutches come stock on production bikes.

Weight will probably increase slightly because of the new gadgets on board—the intake system, four-element slipper clutch and two shorty catalytic converters. Titanium is used extensively in the exhaust system to help offset this. Last year's claimed weight was 381 pounds. You know the old story: The sales department wants the specs out in time to hit the headlines on schedule, but the production people are still fine tuning a few things before the lines start up and the air wrenches chatter. As a result, we get info with some blanks in it, saying “TBD,” meaning “To Be Determined.” When you get your bike, throw it on the scales and let us know.

Chassis changes: Cast areas such as steering head and swingarm uprights have been made more rigid, while extruded parts have been made less so. The swingarm-pivot height has been raised 3mm. Wheelbase is unchanged at 55.7 inches.

The fork has 43mm tubes as before, with marginally larger damping pistons. Steel tube wall thickness has been slightly reduced and the axle-holders (the big cast lumps at the bottom that carry the axle and brake calipers) have been beefed up. At the rear, swingarm torsional stiffness is up 30 percent but the arms are laterally more flexible. Both these measures tend to make the bike feel more hooked up at full lean in turns, when lateral flexibility is providing most of the suspension. In Yamaha's words, the chassis changes are aimed at providing improved corner-entry front-end feel. A relaxed, confident rider is a better, safer, more able rider.

Steering feel stiffens as speed builds because everything spinning up front is a big gyroscope that resists your efforts. Last year's R1 front disks were 320mm but now are cut to 310—a small but useful reduction in gyro mass. The calipers, which were one-piece forged four-piston units, now sport six pistons. With six pistons, the pads are longer and narrower, so the centerline radius of their action (and so, brake torque) is said to be the same as before.

R1 has been a pioneer in the process of making engines more compact front-to-rear by vertical stacking of the gearbox shafts. This allows engine mass to be concentrated forward—useful in itself to keep the front wheel down and steering. It also allows a longer swingarm to be used. This is useful because the smaller the angle through which the arm swings, the easier it is to maintain consistent rear suspension anti-squat. Bikes that squat at the rear during off-corner acceleration tend to lift their front wheels, making the bike run wide. Many small details add up to state of the art. The intensity that has so refined 600cc sportbikes is now coming to the

1000s.

Here's hoping next year's AMA Superbike season is a hot one with the possible return of a major player with an all-new machine. How 'bout it, Yamaha?