Bimota SB3

 

 

 

Make Model

Bimota SB3

Year

1979-82

Production

402 units

Engine

Four stroke, transverse four cylinder, DOHC, 2 valves per cylinder

Capacity

987 cc / 60.2 cub in.
Bore x Stroke 70 x 64.8 mm
Compression Ratio 9.2:1
Cooling System Air / oil cooled

Induction

4x 28mm Mikuni VM 28 SS carbs.

Ignition

Battery, dual points

Starting

Electric

Max Power

64.9 kW / 87 hp @ 8200 rpm

Max Torque

84.3 Nm / 8.6 kg-m / 62.2 lb/ft. @ 6500 rpm
Clutch 15 plates, wet

Transmission

5 Speed

Final Drive

Chain
Frame Chrome molybdenum steel

Front Suspension

38mm Marzocchi forks. 100mm wheel travel

Rear Suspension

Single shock. 142mm wheel travel

Front Brakes

2x 260mm discs

Rear Brakes

Single 260mm disc

Front Tyre

3.50 V18

Rear Tyre

130/80 V18
Seat Height 743mm  /  29.3 in.

Wet-Weight

219 kg / 483 lbs

Fuel Capacity

14.7 Litres / 3.9 US gal

Top Speed

225 km/h / 139.8 mph

Motorcyclist  review

To back-road corner-carves the name Bimota is well known. The Cafe Racers is spoken of in hushed nes as if it were some form of diety. Hundreds lust after this, the most radical and expensive of street machines. Surprisingly, only a tiny handful of the adoring masses have ever actually seen a Bimota Suzuki in the flesh. A glimpse of a photo or a small knowledge of the parts that make a Bimota SB3 seem to be enough to put most mere mortals under the bike's spell.

And it's no wonder. No motorcycle we know of blends such nice parts with such attention to detail. Bimota, an Italian firm, builds the entire rolling chassis, and you supply and install a Suzuki GS1000 engine, carbs and electrics. The result is the closest thing to a street-legal roadracer in existence.

That is, if you have a rather large stack of money. Since there is no one currently distributing Bimotas in the United States, getting an exact price is next to impossible, but it's safe to say that the SB3 rolling chassis would set you back $7000, and maybe more. And of course you must also buy a GS1000 engine to power it. No one ever said owning a modern legend would be cheap.

Being long-time Bimota fanatics, we were really pumped at the prospect of getting our first three-dimensional look at the SB3. The bike had to stay in its crate for photo purposes for a while after we received it, but we wasted no time shoe-horning between the tangle of boards and rope to get an early sample of the riding position. After we grew weary of making engine noises and nearly tipped over the crate with mock cornering gymnastics, we took a close look at what the Italian engineers had wrought.

The brilliant red frame is the heart of the bike's trickery. The chrome-moly tubing encases the Suzuki powerplant around the outside instead of cradling it underneath. The fit is so close that for engine installation and removal, the frame splits into two halves. Two precision conical joints join the halves on either side above the engine, which acts as a structural member.

The SB3 chassis appears to be tremendously strong since heavily stressed areas are well triangulated. The finish of the frame is first-rate too. The chassis incorporates several things normally reserved for exotic hand-built racers. First, there's the single shock rear suspension. At first glance the Bimota's set-up looks like Kawasaki's Uni-Trak dirt-bike suspension, but really it's significantly different.

The shock mounts to the swing-arm at its lower end and to a frame-mounted aluminum bell-crank at its upper end. A connecting link mounts to the front end of the bell-crank and extends downward to attach to the swingarm in front of the shock. If it sounds complicated, that's because it is. The object of all this monkey-motion is pretty simple, though. This system (like Kawasaki's) provides a rising rate, so the further the suspension compresses, the greater the shock's leverage advantage becomes.

This means that the rear suspension gets stiffer the farther it compresses. Bimota wasn't content to rely solely on geometry to provide the progressive action they wanted, so they fit the shock with a progressive spring too. The gas shock also
has adjustable spring preload and adjustable rebound damping. To change the preload setting, the shock must be removed, but the damping adjuster at the unit's upper end can be turned with the shock still in place.

This unique single-shock system controls an even more uncommon swingarm. Instead of pivoting just behind the engine, the SB3's arm straddles the engine cases and pivots on the countershaft's axis. Four sturdy frame tubes converge on each side to provide a rigid mounting point for the arm outboard of the engine cases. It pivots on tapered Timken roller bearings. With the concentric swingarm pivot and countershaft sprocket, Final Final Drive chain tension remains constant during rear suspension movement.

The chain can be run with a minimum of slack to cut down on wear and Final Final Drive-train lash.

Up front, the SB3 doesn't display quite so many innovations. A conventional Marzocchi telescopic fork slides into Bimota's own aluminum triple clamps.

The steering axis is extremely steep—somewhere around 23 degrees—but the triple clamps are bored at an angle to hold the fork tubes at a more conventional angle. Eccentrics in the steering head let you set the steering axis at either of two angles. Bimota-made adjustable clip-on bars clamp to the fork tubes above the upper triple clamp and come with a Brembo master-cylinder in place. You must supply the clutch lever and switch assemblies.
The chassis is such a thing of beauty that it's almost a shame to shroud it in fiberglass.

The bike has a full roadrace-type fairing, but with lights and turn signals incorporated into the design. The stock Suzuki headlight and instruments bolt directly to the mounts inside, while Bimota's own turn signals blend smoothly into glasswork that looks suspiciously like the down-force spoilers on Suzuki RG500 roadracers.

The fairing's aerodynamically clean closed bottom comes within one-half inch of the ground when the bike's suspension is fully compressed. A one-piece body functions as both a cover for the small steel fuel tank and as a seat base and tail section. The area under the seat where you would normally expect to find the battery is occupied by the rear shock and its associated linkage, so the stock GS battery is located just in front of the seat, behind the steel tank.

Getting the SB3 out of the crate and onto the road took a long Saturday, with time-outs to marvel at the machine's beauty and argue over who was going to get to ride it first. There were a few hassles. No provision was made for mounting the horns, so we were forced to improvise.

The aluminum Bimota shift linkage was reluctant to clear the frame, peg bracket and rider's foot simultaneously, and required some grinding. And the stock GS speedometer Final Final Drive had to be machined to fit the Bi-mota/Campagnolo magnesium front wheel despite following the instructions exactly. We clamped Uni foam air filters onto the stock Suzuki carburetors and slipped the reasonably quiet Bimota four-into-one exhaust system in place. To compensate for the Suzuki's now lean carburetion brought on by reduced intake and exhaust restriction, the carbs were re-jetted.

The stock No. 56 main jets were swapped for much larger No. 120s and the needles were raised all
the way.

This was the bike's finest hour. It was complete—ready to ride. And so far, it had lived up to its reputation. We gazed at its curvaceous silver fiberglass and squinted as the low afternoon sun highlighted the gold painted magnesium wheels. One staffer proclaimed the SB3 the most appealing mechanical device he had ever encountered. Others agreed.

Then we rode it and the appeal began to fade. Only a little at first, but the SB3 had definitely started its slow roll off the pedestal and into the Real World.

The riding position is straight off of a roadracer, only it's more uncomfortable since the extra-long reach to the bars puts most of your body weight on your arms. The seat contributes more discomfort by forcing your hindquarters to conform to it instead of the other way around. Of course the whole point of a bike like the Bimota is to create the ultimate street-going roadracer.

We like that idea just fine, but we don't believe that you need to be uncomfortable.
Once resigned to the torturous seating position, we aimed the SB3 at the nearest twisty road. On the way we found that the bike is significantly faster than a stock '79 GS1000-partly due to the less restrictive pipe and air filters, and also due to the Bimota's lighter weight. All that magnesium, chrome-moly and aluminum pay off with a 79-pound weight reduction compared to a stock GS1000E. At 483 pounds wet, the SB3 has far less weight to accelerate.

The bike's smaller gas tank accounts for 10 pounds of its advantage. Even with its stock engine and slightly taller-than-stock gearing, it out-accelerated a 1980 Honda CBX. The Bimota would probably run in the mid-elevens at the dragstrip.

The city streets and freeways leading to our favorite curvery revealed the bike's second major shortcoming. The suspension at each end is much too stiff. The Marzocchi front fork has a corner on the stiction market and refuses to respond to any but the biggest bumps. Seams and lips in the pavement come through the narrow clip-ons full force. The fork strokes only four inches, but it feels more like two. Believe it or not, the front end is downright plush compared to the rear suspension.

No one on our staff has ridden anything short of a hardtail that was as harsh as the SB3. The shock's spring tension and preload seem' about right, but the damping is so excruciatingly stiff that each bump, seam and twig is transmitted to the rider's spine in complete detail. It's fairly common to have the Bimota bounce your feet right off the footpegs when you're unlucky enough to run over a rough section of pavement.

And the seat ensures that it's more than just your feet that get rattled around. Perhaps the SB3 is Italy's latest answer to planned parenthood.
After a thorough bludgeoning aboard the bike, we figured that we'd just back down on the shock's adjustable damping to smooth the ride out. We checked and it was already on the softest setting. We looked at each other in utter disbelief.

Just for fun, we clicked the damping up all the way, but a push-on-the-seat test showed the damping resistance to be about double what it had been. None of us had the courage or desire to ride the bike in that condition, so we set the damping back to full soft and learned to stand up at the first sign of bumpy ground. We theorized (and hoped) that the rigid suspension was intended to make the bike a better handler in the corners. We knew better, but we weren't ready just yet to admit that the Ultimate Cafe Racer might be seriously flawed.

Its appearance definitely isn't. Nothing we've ridden gets more long stares than the SB3—from civilians and police alike. As far as most police are concerned, the Bimota Suzuki is rolling probable cause.

They figure that if you aren't breaking the law right now, you either just finished or are in the process of planning your next transgression. They're probably right, too.
Save your big sins for the curvy roads where the SB3 is at its best. The steering is light, nimble and almost completely neutral. Whatever you might like to try, the Bimota is willing to go along. So if the turn tightens up a bit more than you expected, just flick the bars and pitch it over farther.

You can lean it over as far as your faith in the Michelin tires will permit and nothing drags. The Bimota feels solid. It responds instantly to your inputs without the mushy, sluggish feel of normal street bikes. Of course it isn't really a street bike—its roots are in racing.

Since its engine is mounted one inch higher than a GSI000's, the Bimota has a fairly high center of gravity.

The only time this is noticeable is when braking while leaned over. In these situations the bike has a pronounced tendency to try to straighten up. This can be easily counteracted by dialing in a bit more lean with the handlebars.
Unfortunately, you can't do much to counteract the SB3's behavior on bumps. No matter how wonderful a bike's geometry is, its handling will suffer if the wheels are constantly being bounced off the ground. In fast bumpy bends the Bimota gets squiggly when its wheels fail to follow the bumps.

The chassis is too sturdy to let the bike wobble, but the overall effect is the same—it frightens you enough to make you slow down.
Slowing down is not what one buys the King of Cafe Racers for. If Bimota had their suspension figured out a little better, you wouldn't have to. Only the suspension keeps it from living up to its reputation—maybe even surpassing it. There's one consolation.

Anyone who has enough money to afford the Bimota SB3 in the first place probably has enough green laying around to get the suspension working perfectly. When he does, he'll have a bike that works as good as it looks. And that's great. M

Off The Record

With so many wobbly motorcycles to choose from, it's kind of ironic that Bimota picked on Suzuki to wrap their chassis around. No one was complaining about the way the stock GS1000 (or the old 750, another basis for a Bimota kit) handled. It would have been very difficult to improve on the all-around good manners of the stocker, and Bimota didn't try with their street racer. Looking at it, I expected the SB3 to rattle its fiberglass and to be uncomfortable on anything but a very busy road.

But I also expected an improvement in handling. That's the Bimota's great disappointment. Although the frame is probably fantastic, the too-taut suspension never gives it a chance to show its stuff. It's ironic that the suspension is the first thing that a Bimota owner would have to modify.

Any Bimota buyer is presumably a tinkerer anyway, although he may find his urge to tinker frustrated. The bike is so cramped that he may have difficulty finding room for an ignition system black box, much less an oil cooler.
The beauty, the careful detailing and the ease of assembly had me believing that the SB3 was the bike of my dreams. I was ready to buy one without ever riding it. Fortunately, I got a chance to ride it before I drained my bank account. After that, I put my checkbook away until I could find something with a better suspension, say a buckboard.

Art Friedman

The Bimota really had me going at first. It seemed to possess all of the attributes necessary to make it my favorite street bike of all time. It looked like a full-on roadracer that just happened to be street legal and its reputation promised that it would handle like one too.

As it turned out, there isn't a lot more to the SB3 than looks and reputation. True, it handles fantastically on glass-smooth curvery, but that sort of pavement is in very short supply. Roads that I used to think were smooth feel like paved Supercross tracks when I'm aboard the Bimota. The bike's fork feels like it's filled with axle grease instead of fork oil, and the rear "suspension" couldn't be much harsher even if a strut was bolted in place instead of the shock. The SB3 is a tremendous motorcycle that is rendered almost unacceptable by its suspension problems.

-Jeff Karr