The Vintage Japanese Superbikes Poised To Follow The CB750 K0’s Climb
Vintage Japanese motorcycle collecting has a familiar problem: by the time everyone agrees a bike matters, the affordable examples are already disappearing. Early Honda CB750 K0s can now live in a terrifying money stratosphere, while correct Kawasaki Z1 900s command serious money.
That leaves buyers searching one rung (maybe two) lower for machines with genuine historical weight and prices that haven’t completely lost the plot. These five Japanese superbikes have the engineering story and period performance to benefit as attention moves down the ladder.
5
Yamaha RD350
Release Year: 1973
The Yamaha RD350 arrived in 1973 with the sort of specification that still makes a modern rider pause. Its 21.2-cubic-inch two-stroke parallel-twin produced 39 horsepower, and the complete motorcycle weighed about 364 pounds. That combination gave the RD350 the sharp, urgent character that helped establish Yamaha’s sporting reputation. It was quick enough to become a fixture in club racing, yet compact enough to serve as everyday transport for riders who didn’t mind carrying a little two-stroke oil. The engine’s appeal also went beyond a peak output figure. A light motorcycle with a lively power delivery asks its rider to stay involved, which helps explain why the RD remains more memorable than plenty of faster machines.
That popularity is part of the reason good ones are now important. Many RD350s were raced or modified, while others received expansion chambers from owners who were certain they’d discovered free horsepower. Every questionable garage tune removed another original example from the future collector pool. Current values for clean RD350s sit anywhere between about $2,000 and $14,000, which remains relatively approachable beside early CB750 K0 money. The bikes most likely to climb are standard-looking examples with the right bodywork and an engine that hasn’t been assembled from three donor bikes and a prayer.
4
Honda CB750F Super Sport
Release Year: 1975
Honda had already changed motorcycling with the CB750, but by the middle of the 1970s the original K-series had begun to look more sensible than sporty. The 1975 CB750F Super Sport addressed that with a longer tank, a neat tail section, and a four-into-one exhaust that gave the bike more visual tension. Honda also altered the chassis geometry and stretched the wheelbase to 57.9 inches. The result retained the civilized character of the CB750 while giving riders a machine that felt more interested in corners. The F’s importance sits in that transition. It showed Honda adapting its landmark superbike for buyers who wanted sharper styling without giving up the usability that had made the original such a hit.
The 44.9 cubic-inch SOHC inline-four made about 58 hp at 8,000 rpm, roughly 10 percent more than the contemporary K model. With a full 4.8-gallon tank, the CB750F weighed a little over 535 pounds and carried a 32-inch seat height. Those figures won’t frighten a current sportbike, but the F’s collector case doesn’t depend on winning a spec-sheet bar fight. It carries the CB750 name and remains far below the earliest K0s in the market. Honda continued developing the F with ComStar wheels and revised exhaust routing for 1977, making the first-generation run interesting to collectors who enjoy detail hunting (especially since values sit well under $10,000). As the K-series halo spreads, a correct first-year Super Sport with its factory exhaust and period trim becomes an increasingly obvious alternative.
3
Honda CB400 Four
Release Year: 1975
The Honda CB400 Four made a different argument for performance. Instead of chasing the largest engine, it used a 24.9ci inline-four producing 37 hp in a lighter, more compact package. Its low handlebar and slightly rear-set riding position gave it a purposeful stance, while the sweeping header and megaphone-style exhaust made the little Honda look far more exotic than its displacement suggested. It encouraged riders to preserve momentum rather than wait for a huge engine to fix a lazy corner exit. That quality gives the CB400 Four a personality of its own instead of leaving it trapped as a scaled-down CB750.
Collectors have already started recognizing what made it special. Current values go up to about $15,000, placing the best CB400 Fours well above ordinary used-bike territory while leaving them comfortably below trophy-grade CB750 K0s. That spread suggests the halo effect may already be working. Original paint and factory-correct exhaust parts matter because this was another bike that owners loved to personalize. A nicely preserved CB400 Four also has a practical advantage over many larger 1970s machines: its performance can be enjoyed without turning every ride into a wrestling match with half a ton of period engineering.
2
Yamaha XS Eleven
Release Year: 1978
The Yamaha XS Eleven came from the opposite end of the scale. It was Yamaha’s flagship, built around a massive 67.2ci DOHC inline-four connected to a five-speed transmission and shaft drive. Yamaha originally claimed 95 hp, which was a serious number for the late ’70s. The later XS11 Special tested at 584 pounds, about 20 pounds lighter than the standard Eleven, and still covered the quarter-mile in 12.15 seconds at 109.48 mph despite emissions-era tuning that had pulled output below the original claim. The Special also used air-assisted forks and adjustable rear damping, showing Yamaha’s attempt to make all that mass manageable. This was a motorcycle designed to flatten distance at speed, rather than to apologize for taking up most of the garage.
That combination of speed and size has probably worked against the XS Eleven as a collectible. It gained a reputation as a fast, capable road bike rather than a delicate piece of sporting jewelry, and shaft-drive machines rarely receive the same romantic treatment as race-replica hardware. Yet that may be precisely why it remains interesting. The XS Eleven represents an era when Japanese manufacturers discovered they could combine superbike acceleration with long-distance ability. Its later Special could carry more than 500 pounds with half a tank of fuel, which sounds less like a sports-machine statistic and more like permission to move house.
1
Kawasaki GPz550
Release Year: 1981
The Kawasaki GPz550 is the clearest bridge between the universal Japanese motorcycle and the modern sportbike. Kawasaki started with the successful KZ550, then added hotter cams and higher compression. Electronic ignition and an oil cooler completed the performance work, while a six-speed transmission helped keep the engine on song. The GPz also received rear-set footpegs and triple disc brakes, along with a small fairing that made its intentions obvious before the engine even fired. Its 33.7ci DOHC inline-four produced a claimed 57 hp at 9,500 rpm, while the motorcycle weighed 460 pounds with half a tank of fuel. A 54.9-inch wheelbase and quick steering geometry gave it the responses expected of a serious middleweight, rather than a standard bike wearing sporty paint after lunch.
The performance figures give the GPz550 its killer collector argument. It ran the quarter-mile in 12.65 seconds at 104.16 mph, only 0.04 second behind the original Kawasaki 900 Z1’s time. That’s astonishing context for a middleweight that listed for $2,599 when new. The GPz550 delivered almost the pace of Kawasaki’s blue-chip icon in a lighter package that handled with far greater precision. It also arrived before full fairings and liquid cooling rewrote the sportbike template, leaving it with one wheel in the UJM era and the other pointed toward the Ninja generation. Look around for one and you’ll be pleasantly surprised, given that most of the auctions see them going for under $10,000. Find a straight, original GPz550 before everyone else notices that it’s been hiding in the Z1’s shadow for more than four decades.
Sources: Classic.com, Cycle World, Iconic Motorbikes Auctions, Hagerty.
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