Unit Pro-Link
Question: How can an innovative rear suspension system make its way from the world-beating Honda RC211V MotoGP bike to the most impressive street rod ever conceived?
Answer: Brilliant engineering is its own reward.
Honda's race team engineers first dreamed up the all-new Unit Pro-Link rear suspension system to enhance mass centralization-a key element in racing-as well as to open up possibilities in frame design. Because the top eye of the shock in the Unit Pro-Link is captured on the top of the swingarm, suspension forces aren't transmitted to the frame. And the frame itself can be opened up or lowered because a sturdy crossmember is no longer needed as a frame attachment point for the rear shock.
Of course, all that is well and fine for racing-oriented machinery, but how does this new-think engineering make a street rod better? The main benefit to the Rune is simply this: Because no rear crossmember is needed on the frame for shock attachment, the Rune's seat can be perched a mere 27.2 inches off the ground. That's about as low as it gets, which means the Rune is as cool as it gets-in this area and just about every other aspect as well.
Like the Unit Pro-Link systems used on the championship- winning 2002 RC211V MotoGP bike and the 2003 Daytona Supersport- dominating CBR600RR, the Rune's shock runs from the top of the swingarm down through the swingarm itself, to attach to a bellcrank linkage system located below. There, a pair of arms attaches the bottom shock eye to the bottom of the frame via a pair of tension links.
As the rear wheel rises in passing over a bump, the pull of the tension links rotates the arms, thereby compressing the shock from the bottom. Even though the shock itself moves upward as the swingarm moves up, a rising-rate ratio in the bellcrank system continues to compress the shock from below. Depending on the geometry of the linkage, the bottom of the shock can move more, and more rapidly, than the top of the shock; hence, the shock compresses.
Also like its sporting cousins, the Rune shock features a remote reservoir to supplement oil capacity in the damper-a bit of high- tech trickery that remains cloaked within the stylish bodywork. But don't fret about not being able to show off this tasty little tidbit; onlookers will still have plenty of eye-candy to enjoy while checking out the Rune.
Trailing Bottom-Link Front Suspension
For a while now, Honda's R&D division has piqued expectations among legions of concept bike fans as they have snared glimpses of an innovative trailing bottom-link front suspension. Now, the faithful have been rewarded as this attention-grabbing front end makes its debut on a production machine, the Rune.
The heritage of the trailing bottom-link runs through a pair of concept motorcycles that were eagerly embraced by forward- thinking fans of the sport. The distinctly futuristic Zodia made its debut in 1995 at the Tokyo Motor Show and the image of this sleek- looking concept power cruiser stayed indelibly marked in the memory of many watchful fans. Two of its more impressive elements: a trailing bottom-link front suspension and a single-sided swingarm- sound familiar? Next up was the T2 model revealed to the public in December of 2000 at a motorcycle show, where this precursor of the Rune was clearly the runaway favorite among three new concept models.
Like these two non-runners before it, the Rune uses twin pushrods to transfer suspension loads through a linkage system. These arms and links actuate what appear to be twin shocks flanking the steering head and headlight. In actuality, the right side contains only the main spring for the front suspension system, while the left shock handles damping duties and also contains a lighter weight sub- spring.
Although the brilliant finish and ground-breaking configuration appear to imply a new kind of suspension sensation, the new trailing bottom-link system has been designed to return a feel and fork action that is entirely familiar to seasoned motorcyclists. There's no need to make special accommodations for this new front end; just ride and enjoy.
Rune Engine
The most impressive looking hot rod ever conceived by Honda had to boast impressive performance credentials as well. So it should come as no surprise that the Rune is the most powerful Honda custom to ever turn a wheel on public roads.
To accomplish this goal, Honda's engineers tackled the task in classic hot-rod style. Beginning with the already massive 1832cc liquid-cooled overhead-cam horizontally opposed six-cylinder engine built in America for the new GL1800 Gold Wing, the engineering design team leaned on this touring-oriented powerplant to boost its power to impressive new heights. Six 32mm throttle bodies with 12-hole injectors replace the twin-body system used on the GL for upgraded fuel flow and a freer flowing system. New camshafts, revised 3-D fuel injection and ignition timing mapping, along with a new close- ratio gearbox all help make the Rune a true road warrior, with more torque than any other two-wheeler around. In addition, a 6.9-liter airbox supplies large volumes of clean, cool air to the engine, and a free-flowing six-into-two exhaust system delivers added power along with a lumpy-sounding and surprisingly authoritative growl that grows to an inspired howl at full throttle.
All of which gives the Rune a full measure of impressive performance to match its impressive countenance.