Back to the Future: 1983 Honda CX650 Turbo

Dean Stuckmann has four Honda turbos – two 500s and two 650s – and this perfect Honda CX650T is the nicest of the bunch.

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by Jeff Barger

1983 Honda CX650TEngine: Turbocharged 674cc OHV liquid-cooled transverse 80-degree V-twin, 82.5mm x 63mm bore and stroke, 7.8:1 compression ratio, 16.4psi max boost, 100hp @ 8,000rpm
Top speed: 139mph (period test)
Fueling: Computerized fuel injection
Transmission: 5-speed, shaft drive
Electrics: 12v, electronic ignition
Frame/wheelbase: Backbone-type with engine as a stressed member, round/box-section mild steel/58.9in (1,495mm)
Suspension: Showa air-adjustable fork with adjustable TRAC anti-dive front, Honda Pro-Link with Showa single shock w/adjustable air pressure and rebound dampening rear
Brakes: Dual 10.9in (276mm) discs front, single 10.9in (276mm) disc rear
Tires: 100/90 x 18in front, 120/90 x 17in rear
Weight (wet): 571lb (259kg)
Seat height: 31.1in (790mm)
Fuel capacity/MPG: 5.3gal (20ltr)/40-50mpg (est.)
Price then/now: $4,998/$4,000-$6,000

At the time, new technologies were launching that changed the way people watched movies and listened to music, and Dean appreciated new technologies such as the Sony Betamax videocassette player and Pioneer LaserDisc player. He still has both of them, set up and functioning, in his home entertainment system.

“I’ve always really been into new technology,” Dean says of his early-adopter status, and that passion carries over to his interest in motorcycles. He continues: “Early in 1981, when motorcycle magazines began running stories about the first Honda CX500 Turbo, I thought the bike was really something special. I went to my dealer, Wickman’s Cycle Service in Manitowoc, so I could be the first to get one.” Dean traded his Honda CB750F and put money down on a brand-new 1982 CX500 Turbo – sight unseen. Part of the deal included the dealer’s wall poster and sales materials, pieces of ephemera Dean continues to maintain in his personal collection. Almost four decades and 77,000 miles later, he’s also still got that CX500 Turbo. But that machine was really just a gateway to his ultimate Honda – the rare 1983 CX650 Turbo.

Turbo fever

We can’t talk about Honda’s CX650 Turbo without first discussing the CX500. Honda launched the CX500 Turbo in 1982 as a technological tour de force, but they were not the first motorcycle manufacturer to use a turbocharger to stuff more fuel and air into an engine for more power. In the 1930s, British and European race teams were experimenting with superchargers – a slightly different method of forced induction where a “blower” takes its power from a crankshaft pulley, compressing the fuel/air charge. A turbocharger, by comparison, uses waste exhaust gases passing over a turbine, which in turn spins a compressor wheel to cram a dense fuel/air mixture into the combustion chamber. The result? Greater power in a smaller powerplant.

Kawasaki, working with California-based Turbo Cycle Co., launched a turbo-powered bike in 1978 with the Z1R-TC, but it was a bike some called a crudely developed concept and didn’t last past the 1979 model. Honda was next with the CX500T of 1982, and it bristled with advanced computer control systems to ensure everything worked as intended. Honda wasn’t alone, as Yamaha was right behind with the 1982-1983 XJ650LJ Seca, and in 1983 Suzuki introduced the XN85. Kawasaki didn’t roll over, coming out with its own turbo-powered bike for 1984 and 1985 with the ZX750E1.

The CX500

In planning for a turbo-powered bike, Honda chose the tried and true CX500 platform. Tough and reliable, the CX500 featured a 497cc liquid-cooled V-twin, placed across the frame similar to a Moto Guzzi layout, and with shaft final drive. The CX500 produced 50 horsepower and weighed just a little less than 500 pounds wet. When the turbo was installed, power was increased to 82 horsepower, and the CX500 Turbo bristled with modern tech, including fuel injection and electronic ignition. Other advancements included Honda’s TRAC anti-dive front brake system and Pro-Link monoshock rear suspension.

Honda issued a corporate statement about turbo development, saying that since the early 1970s Honda had been considering transportation “priorities” that would exist by the 1980s. Honda’s statement noted that the “new decade would demand increased efficiency,” adding that “engines displacing less than 1,000cc would take on major significance due to their fuel efficiency. Yet the modest power ratings of these small engines suggested that accepted levels of acceleration and performance would have to be compromised at the same time.”

Not so, decreed Honda engineers, and two goals were set. “First, the creation of technology that would exploit the fuel efficiency of small engines without sacrificing acceptable levels of performance. And second, the embodiment of that technology in a new kind of high-performance vehicle. The Honda CX500 Turbo meets the challenge of the Eighties by combining fuel-efficiency with high performance,” Honda said.

“I got a great kick out of the CX500 Turbo,” Dean says. “But it wasn’t perfect by any stretch. It’s a little sluggish in the lower rev range, and then the turbo comes on like a sledgehammer around 5,000rpm. I learned this on my initial ride home from the dealer – I cracked the throttle open to pass a car and the bike was a real dog for a couple of seconds, but then it came on so hard I almost rear-ended it. Turbo lag is the main fault of those bikes, and it makes it difficult to ride them fast – especially when you’re coming out of a corner. I was never a really hard rider, but I understood the eccentricities of the model.”

The CX650 Turbo

Honda took what it had learned developing the CX500 Turbo, and in 1983 launched the upgraded CX650 Turbo. “Many of the 500TC’s shortcomings arose from its modest displacement,” an October 1983 article in Cycle magazine said. “Off the boost, it felt somewhere between a normally aspirated 250 and 400. Honda has logically increased the displacement of the CX-Turbo, and as a 650 the CX-T has considerably greater off-boost power than the old 500 or the Yamaha and Suzuki 650 Turbos. Consequently, the Honda is a pussycat in town. Once the engine hits the boost, however, the CX turns into an absolute animal with stunning mid-range punch. In roll-on contests from 60mph against the Superbike King, the Suzuki GS1100, the Honda easily jets away,” Cycle said.

The CX650 Turbo (and its non-turbo siblings, the CX and GL) featured an 82.5mm x 63mm bore and stroke to displace 674cc. While the 500 turbo ran a 7.2:1 compression ratio, the 650 was bumped to 7.8:1. Also increased were valve sizes, with intakes going from 31mm to 32mm and exhausts from 24mm to 28mm. While the 500 and 650 both had pushrod-actuated four-valve-per-cylinder heads, the 650’s had larger intake ports and injector bores, and the intake valves stayed open longer.

Built by IHI to Honda specifications, the turbocharger on the 650 was slightly different than the one first used on the 500. For example, the 650 turbo had a 3mm larger compressor wheel at 51mm in diameter, although the exhaust turbine stayed the same diameter at 50mm. The waste gate on the 500 would open at 17.4psi of boost, while the 650 had been lowered to 16.4psi.

The engine serves as a stressed member in the backbone-type steel frame that features an aluminum swingarm at the rear with a single air-adjustable shock. The front end is anchored by an air-adjustable fork with 37mm tubes and Honda’s TRAC anti-dive valving. An upgrade over the 500 Turbo was a new fork brace.

Dean notes that there were many more differences between the 500 and 650 Turbos, including the fairing, mirrors, windscreen, handlebars, switches and controls, fuel injection system, final drive, exhaust, seat, rear grab rail, tail cowling and rear fender. While the 500 and 650 machines look almost identical, except for color, there is very little that is truly interchangeable between the two.

Although the CX650 Turbo was all around a better bike than the 500, Honda’s experiment with turbocharged bikes ended just two years after it began. Why? Liter-sized bikes were able to do everything a turbo could with less technology, making them cheaper to produce and ultimately less expensive for the consumer. Fewer than 1,200 CX650 Turbos were brought to North America – its biggest market – out of a total production pegged at 1,777.

“I feel that these machines were under-appreciated at the time,” Dean says of the CX500/CX650 Turbos. “It took some guts for Honda to think outside the box and create these technological marvels. Maybe they were just ahead of their time.”

Up close

Dean knows the Honda models well, having ridden his original 1982 CX500 Turbo from new until 2000. During that time, he replaced two stators, a component he says is a weak link in the model, and here’s why: Both turbo and non-turbo CX engines are water-cooled. However, the turbo itself is oil-cooled, and unlike the water-cooled turbos of today, Honda relied on just crankcase oil to cool the turbo charger. Dean believes Honda knew this could be a problem, as they added a finned external oil sump to the bottom of the crankcase to aid cooling, but that wasn’t enough to bring oil temperatures down. The stator is bathed in engine oil, and the higher oil temps wreaked havoc on the stator insulation, which would fail, causing the stator to short out.

After 50,000 miles, he also needed to replace the clutch basket, and because parts were becoming difficult to find, he went in search of a parts bike. At a salvage yard in Green Bay, Wisconsin, he found two crashed CX500 Turbos. One had been laid down on the left, the other on the right. Included was a new-old-stock fairing; he bought the package.

Back home, looking at his three CX500s, he realized he could build a very nice example that he could ride on Sundays, plus have enough parts left over to still have a daily rider Turbo that he could continue to ride on his 8-mile commute to work. Then, late in 2003, he found the Honda he really wanted – a 650 Turbo.

“I’d always yearned for a CX650 Turbo,” Dean tells us, “and I would occasionally see one for sale on eBay, but they were usually a long way from home. Eventually, I found one for sale in Wisconsin that needed some work, and I bought it and fixed it up.

“Not long after that, I told a local ex-Honda mechanic friend of mine that I finally bought one – only to find out that he’d purchased an excellent example only five days earlier! I don’t think there were any CX650 Turbos in Manitowoc County for 20 years and now there were two within a week. We compared bikes, and I asked him to give me first dibs if he was ever going to sell his.”

When Dean was offered the CX650 Turbo for $3,800 in early 2004, he snapped it up. It was in excellent condition with low miles, and Dean felt it needed only some detailing to bring it to an exceptional standard. He got the opportunity to do just that only a few months after buying the Honda, when the stator failed. “I’ve done stators numerous times and I was getting to be an old hand at it,” he says. “To replace the stator, the engine has to come out of the frame, so while doing that I took my ‘new’ CX650 Turbo down to the bare frame to detail everything.”

Dean pulled every component and cleaned everything he could get his hands on, including the wiring harness. With the exception of the exhaust and one Turbo emblem on the engine, which Dean painted, nothing was sprayed, plated or powder coated. To detail fasteners, he quickly passed them over a buffing wheel – not to polish them, he says, but just to clean up the surfaces. “There were lots of cleaning solutions and waxes used on the majority of the components,” he says.

Most of the engine was left together as it was in fine fettle, and the only replacement parts included an aftermarket stator from Electrex and new tires and brake pads all around. Detailing the CX650 Turbo was a time-consuming process, but the result is a very close to factory-fresh machine, as Jeff Barger’s beautiful photographs clearly show.

If you’re keeping track, Dean still has four Honda turbos: two 500s and two 650s. One of each size is a relative show bike that will see occasional use. The other two were once daily riders that have been parked for a few years, and while still complete, are now considered parts bikes. Dean put 77,000 miles on his first CX500 Turbo, and after doing some calculating, he figures he’s put 20,000 miles on each of his other three. That’s a total of 137,000 miles on Turbos since 1982. “After all these years, the feelings I get as the turbo spools up to max boost still brings a smile to my face,” Dean says. “Is there a better reason to ride than that?” MC

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