09/10/2025
BIDRIDER- TURBO TIME!
2 of the 4 Turbo bikes produced in the 80's
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1. 1983 Suzuki XN85D Turbo
After Yamaha and Honda released their turbocharged motorcycles in 1982, the Japanese Turbo War became increasingly inevitable. Shortly after the launch of the Honda CX500 Turbo and Yamaha XJ650 Seca Turbo, rumors from Japan suggested that Kawasaki was preparing a prototype turbo engine that would be even more powerful than those produced by Honda and Yamaha. The bad news was that Kawasaki's development took much longer.
Hearing the opportunity, Suzuki immediately stepped forward as the next competitor in the Turbo War. The concept of this Suzuki turbo motorbike was first introduced in 1981, at the Milan Motorcycle Show. And miraculously, Suzuki was able to perfect the prototype motorcycle into a full-fledged product in just two years.
Its name is the Suzuki XN85 Turbo , a forced induction engine motorcycle released in 1983, and that same year it was immediately brought to the blue continent market. The price at that time was set at around $4,700.
The design borrows from the iconic Suzuki Katana half fairing . This bike looks great! It doesn't look too tourer-y like the Honda CX Turbo, and it doesn't look overly oversized like the Yamaha Seca Turbo's alien design.
the basic engine is taken from the GS650E with a 4-cylinder, DOHC 2-valve per cylinder configuration with standard air cooling. Then, like Honda & Yamaha, Suzuki also strengthened almost all of the GS650's internal components before installing it on the XN85 Turbo.
In addition to replacing the internal engine components, Suzuki also added a fairly large oil cooler for this motorbike. In addition, they also added a kind of oil spray channel behind the piston to help cooling. This technology was later known as SALCS (Suzuki Advanced Lubrication & Cooling System)... And there is still a Ram Air System that is used as a cooling air flow to the cylinder head. The Suzuki XN85 Turbo does not use a radiator like the CX500/650 Turbo.
Why is Suzuki so serious about cooling its engine? Well, there's a reason. Suzuki uses a turbo from the CX500 made by IHI (RHB51B) which has a 50mm diameter propeller. And because Honda seems to be cheating by using water-cooling technology , Suzuki, which still uses traditional technology, is forced to scratch its head to cool the turbo and its effects on the XN85 engine.
The first trick they did was reduce the turbo's boost pressure, from 19 psi in the CX500 Turbo to a maximum of 9.6 psi in the XN85 Turbo.
But what makes it confusing next, because the size of this Turbo is designed to be placed in the V-Twin engine space, Suzuki is confused about where to put the IHI Turbo? And because we are discussing Suzuki, an underdog manufacturer that is being chased by a Turbo motorcycle production deadline, they then put the turbo behind the engine, right above the gearbox, aka without any air cooling flow at all.
Next, because they don't want to be left behind by Honda who uses sophisticated electronic technology, they also use Fuel Injection from Mikuni-Bosch L-Jetronic. The difference is, because they don't have the computing expertise like Honda, automatically the Suzuki XN85 Turbo only uses sensor parameters equivalent to those of the Yamaha Seca Turbo. But, even though the combination of injection sophistication & simplicity of its application in the XN85 Turbo sounds very promising... This engine becomes very complex if we discuss it as a whole.
And to make matters worse, the turbo's placement, which lacks any airflow, also makes the already hot engine even hotter. And when the air pressure gets hotter, performance automatically drops even further. Suzuki is so serious about this problem that it even includes an oil temperature display on the XN85 Turbo's speedometer as a reminder to the driver.
Given only three years for development until release, Suzuki was forced to re-tune its engine to a more docile character. The goal was to alleviate concerns about engine durability, a concern Japanese brands, especially Suzuki, place a high premium on. They didn't want their bikes to be perceived as easily damaged by consumers.
This strategy proved to be Suzuki's biggest mistake after the RE5 era, which failed miserably in the market. The problem was that downspeccing the engine meant a reduction in power! Despite its minimal turbo lag, the XN85 was far inferior in terms of performance. So inferior, in fact, that the XN85 was still inferior to Suzuki's non-turbo motorcycle at the time, the GSX750, which was faster, lighter, and much cheaper.
Some of you may be wondering why it's called the XN85, even though its engine capacity is only in the 650cc class. Well, this is because Suzuki claims the power output of this motorcycle is 85 HP. This 85 is the origin of the name Suzuki XN85 Turbo. This was criticized by several British magazines who called this motorcycle the XN75, because its power output felt more like 75 HP—lower than the naturally aspirated 700cc motorcycles of the time.
The performance of the Suzuki XN85 Turbo was so low that Suzuki America seemed to hide the existence of this turbo motorcycle from consumers. This is why this motorcycle is often called Suzuki's stepchild.
What's even more painful for the "stepchild" nickname is that Suzuki is quietly developing a 750cc sportbike with a new generation TSCC 4-valve engine, which will be named the GSX750. This bike is not only cheaper than the XN85 Turbo, but also able to match its claimed power output, while being much lighter too. Naturally, any sane consumer will definitely choose the GSX!
So, with development costs of millions of yen for the XN85 Turbo, Suzuki only produced 1,153 units of this bike during its production run! This is significantly fewer than the Yamaha Seca Turbo and Honda CX Turbo.
2. 1983 Kawasaki GPZ750 Turbo
In 1983, Honda, Yamaha & Suzuki shook the world 2-wheeled market with Turbocharged motorcycles that had fantastic technology & details for their era. Honda started this mass-produced Turbo class with the CX500, then Yamaha answered with the XJ650 Seca Turbo , which was answered again by Honda with the CX650 Turbo , and finally made an anti-climax with the presence of the eccentric Suzuki XN85 Turbo.
Unfortunately, this concept hasn't caught on with consumers, who prefer larger , naturally aspirated motorbikes over their turbocharged counterparts. Naturally aspirated motorbikes are cheaper, lighter, more agile, simpler, more efficient, and offer comparable performance and horsepower. So, why buy a turbo motorbike that's much more complicated and offers no significant benefits?
Well , the question above applies – except for this turbo motorbike from Kawasaki… Which has a different concept compared to its 3 competitors from Honda, Yamaha & Suzuki.
The first thing that sets Kawasaki's Turbo motorcycle apart from the others is its base. Yamaha and Suzuki make turbo motorcycles based on 650cc 4-cylinder engines. Honda has a slight advantage with its 4-valve, radiator-cooled engine, but unfortunately, its V-Twin engine configuration is more aimed at tourers.
Well, when Kawasaki started this motorcycle project in the late 1970s, they actually used the KZ650's 650cc 4-cylinder engine as their base. But after a year of development, the green gang realized, as if saying:
"Hang on a minute, if we make it using the Z650 base, it will be just as slow as the others, right? What the hell is this!" And because Kawasaki really doesn't want to be labeled as a manufacturer following in other people's footsteps... A year later, the concept was immediately changed.
Instead, Kawasaki completely overhauled the KZ650 engine with a larger piston, stronger crankshaft & piston rod, more advanced camshaft duration, plus a larger RPM limiter. Simsalabim , a new engine with a capacity of 738cc, aka entering the 750cc moge class. Now the advanced version of the engine tuning will be the basis for the green gang Turbocharger engine... While the stock version is also available, released under the name GPZ750.
The stock version, called the GPZ750, was released first in 1982, while the one with the Turbo had to undergo much more extreme testing, so the release moment was delayed quite a long time. In April 1983, the green gang secretly invited journalists to try out their Turbo motorbike at the Salzburgring circuit, Austria. The motorbike was originally called the Kawasaki 750 Turbo , very simple. But over time, the 750 Turbo was also often called the GPZ750 Turbo or ZX750 Turbo.
The ZX750 Turbo has very simple details. The design uses a full fairing inspired by the GPZ900R project, the chassis is taken from the standard GPZ750, plus all the suspension settings are made stiffer & the front suspension rake is made more stretched to maintain stability at high speeds when boosted by the Turbocharger. Different from the Seca Turbo, the ergonomic ZX750 Turbo is made without the slightest compromise.
Even though it was introduced in 1983, Kawasaki only officially sold this motorbike in 1984. Because it was different from Suzuki which seemed to be chasing a deadline , Kawasaki had to perfect the power delivery & durability of its 4-cylinder engine from the Turbocharger boost.
the ZX750 Turbo uses an identical engine base to its non-turbo version, the GPZ750. But unlike the super-bar-bar Z1R-TC – because the ZX750 Turbo is sold in bulk and has a warranty – automatically the green gang has to strengthen the internal parts of the engine… Just like what Honda, Yamaha & Suzuki did.
The difference from the 3 Japanese manufacturers above, Kawasaki really pays attention to all the details in this motorbike. As a Turbocharger supplier, Kawasaki collaborated with Hitachi to create a small turbo with an inlet diameter of 47mm. The maximum boost pressure is set at 10.5 - 11.2 Psi before the wastegate opens. This is bigger than the Seca Turbo & XN85 Turbo duet. And because the engine uses 4 cylinders compared to Honda which still uses V-Twin, automatically the manifold pressure of the ZX750 Turbo is also much bigger than the CX Turbo.
Then, learning from the mistakes of previous 4-cylinder turbo motorcycles that placed the turbo behind the cylinder, Kawasaki made a brilliant breakthrough by placing its turbo directly in the exhaust header area. Automatically, the turbo gets direct cooling from the front, while also spooling faster due to the close proximity of the exhaust port and the turbo unit.
Kawasaki also uses electronic fuel injection from Mikuni, so the throttle response isn't as slow as the Seca Turbo. And combined with a well-placed turbo, a larger engine capacity, and excellent engine tuning, the Kawasaki ZX750 Turbo has become the turbocharged motorcycle with the least turbo lag – and the most powerful turbocharged boost sensation compared to the other Japanese trio.
What's even more amazing is that this Kawasaki isn't just outdoing its three competitors in terms of engine and turbo details. There's something else that makes the ZX750 Turbo often called the best of the Japanese Turbo War era. Want to know why? Well, the answer lies in the basic concept of the ZX Turbo itself. This motorcycle doesn't come as a corporate statement like the Honda CX Turbo, which boasts Honda's signature alien technology. It's also not like the Yamaha Seca Turbo, which seemed more like a response to Honda, rather than to consumers. And of course, the ZX Turbo isn't like the Suzuki XN85 Turbo, which was half-developed to keep up with the hype. The Kawasaki ZX750 Turbo comes as the successor to the Z1R-TC, offering a wild performance sensation and high excitement.
The Kawasaki ZX750 Turbo is claimed to be capable of spewing out a maximum power of up to 112 HP – and torque that almost touches 73.1 ft-lb. That means, the claimed power of this motorbike is much greater than the CX650 Turbo, Seca Turbo, CX500 Turbo, let alone the XN85 Turbo. Heck , even the claimed power is not much different from the GPZ1100 which is two classes higher. And what's even more terrifying, this ZX750 Turbo doesn't just rely on the brochure specifications.
the ZX750 Turbo is not the most powerful for circuit racing… But according to reviewers who tested this bike directly, the ZX750 Turbo is capable of embarrassing the 1000cc superbike class when competing on a drag race track. Based on the test, the fastest time achieved by the ZX Turbo was able to break through 10.71 seconds on a 402m track – by Jay Gleason. It was so fast, even journalists were able to break through 11.2 seconds on a standard ting-ting motorbike… The exact same time record as the GPZ1100 when driven by professional testers.
And that, my friend , is the true turbocharger effect. While Honda, Yamaha, and Suzuki have failed to produce turbocharged motorcycles with performance levels exceeding those of the naturally aspirated 750cc-900cc class, Kawasaki has instead dared to challenge the performance of the 1000cc class and above.
As a result, even though turbocharged motorcycles were considered unpopular with consumers at the time due to their high prices, sophisticated technology, and mediocre performance… The Kawasaki ZX750 Turbo was still able to sell more than 3,500 units in the United States market. The crazy thing is, most of those who bought it actually modified the turbo wastegate settings, so that it was said that at that time its power was able to match the power output of the Z1R-TC!
