CBX, Z1300, Sei - The Six Pack Trio

The 70s saw something or had something which was never replicated on any era previous or later to it. It was in the 70s that Benelli, Honda and Kawasaki released 6 cylinder engines for mass production. 6 cylinders were something never heard of before the mid 60s and even now, barring the Honda offspring like Rune, Goldwing or the prototype Evo6it is difficult remember any machine with 6 cylinders. And way back in the 70s, people had a choice of 3 superb engineered machines.
Of course, the most famous of the trio was the HONDA CBX, a bike as legendary as the brand itself. Honda came to the world in full flow in the early 60s and had established themselves with the CB series, the 750, 550, 400-Four and the likes. But through the late 60s and early 70s, Honda didn’t do much except giving newer versions of the same bikes. There was nothing new, in fact Honda was known for innovations, but these years, Honda was up to nothing. Or was it?
Mr. Tadashi Kume, the then Director of Honda Research and Development knew the unrest among Honda and in general motorcycle fans.
There were rumours speculating and everyone knew that Honda was upto something, but nobody had any clue as to what it is. So Kume then released it… the world’s fastest bike ever produced, the Big Daddy of all, a brute 1047cc, 24 valve with four overhead camshaft, the CBX-Six. The bike was Godzilla fast. The letters CB followed by a bigger X became known all over the motorcycling world as a must-have commodity, the bike to own and certainly the bike to ride. This was a standard everyday bike which was an excellent tourer, very very fast and all sorts of things you would have wanted in a bike in the 70s. This was ‘it’. Critics revved its technical credentials, the masses lapped it left and right.
So how did it come into production? Well, Honda had their 250cc and 300cc 6 cylinder GP race engines designed by Shoichiro Irimajiri. He was the project leader of the CBX and believe it or not, he had designed a 2 stroke bike (of course GP spec) which went all the way up to 23000 rpm from its puny 50cc engine! He also designed a 125cc five. At those times Yamaha and Suzuki were ruling the charts with the killer 2 strokers and to be competitive, Honda had to bring in the 5 and 6 cylinder bikes. The CBX-Six is a direct descendent of those race engines. So, the CBX took only 18 months for production. But the results initially showed that Honda has been rather too quick. There were issues but the world knew that the CBX is going to be the one bike which will turn on a new era in motorcycling.
The CBX in the prototype stage had 2 models the one which came out and another with four cylinders which was also had a 1000cc motor. The in-line four produced 98 horses inside compared to 103 (measured at the crankshaft) for what eventually came out. So why was the 6 preferred? Simple because it sounded good!, Actually, because since the engine size was same, obviously the 6 would have a better delivery of power. And of course, it sounded good!

Okay, now how to fit the massive engine? Irimajiri bought Norimoto Otsuka (Honda's Chief Designer for Honda motorcycles sold in North America and Europe) on board. Lots of thinking, engines tilting forward, need of cornering clearance as it being a high-performance sporting bike and all, the CBX fought through all these.
What came out was something exceptional. The bike was blindingly fast, but it was so smooth, that one won’t even notice it if not for the speedometer. The torque was even and linear. It was capable of very high speed handling and remember! this was not a sports bike, but rather a standard road bike. The point is that it was capable of everything.
Extremely comfortable seats, easy handlebars and there was even a covered fuse box mounted on the top triple clamp. Lots of power from the big engine and thanks to the in-line 6, there was no mentionable vibration. But it never made the rider forget that it is indeed a big heavy bike. So it also needed an experienced rider. Well, Honda had that thing in mind that the CBX was meant for experienced riders. You can well imagine how big the engine will be and corners are not going to be easy… but actually Honda thought about that too. You see, when 1000cc is released by 6 engines instead of 4, the engine sizes are smaller and by law of physics, a Six with a three-into-one exhaust can get by with smaller, lighter mufflers than a comparable Four, and smaller mufflers have less of a chance to drag the ground than larger ones. To reduce weight of the bike, some of the essentials were made of aluminum like triple clamps, spoke wheels or plastic like the front fender, had tubeless tires, wet sump instead of dry sump, etc.
Okay, we all know about the CBX more or less, right, so let’s get to some interesting and relevant stuff. The front brakes were of entirely another world. As mentioned Honda knew that by and large, the Honda CBX would be bought by experienced riders, the lightweight, 5mm-thick front rotors are from the GLl000; the rear rotor is unique to the CBX and has been thoroughly trimmed for lightness. Front calipers are from the 750, the rear is the same as the GL's. What makes the CBX's front brake unique is its extraordinarily powerful, light action. A very interesting thing is that initially, the Honda engineers spent days at a air base center in Japan recording the sound of Phantom jet fighters and then replicated the exact sound on the CBX. But later Mr. Kume rejected Irimajiri’s concept and the exhaust note was changed to make a more Porsche like sound! On the performance front, it is a fact that the bike can accelerate uphill from 15 mph in fifth gear without a hitch and just like that, it can twitch and turn in mountain roads like a 400 pound bike when it tipped the scales at almost 600 pounds. It had its shortcomings, well if you can call them that, you see, it was kind of a guzzler 35mpg, but that was expected, the other thing was that your mechanic would not really like fiddling with 24 valves each time you wanted a thorough service or he won’t like re-synchronizing the six carburetors either. Such a massive bike with extraordinary front brakes also meant frequent tyre changing, but the fact is you knew what you are getting into, there were no surprises and probably for all these reasons, Honda expected the CBX buyers to be the mature experienced type. All in all, here was ‘the’ bike, devastating engine performance, brilliant high-speed handling, great cornering capabilities for a bike of this stature and many a critics has compared it to GP bikes, but why not, after all it was derived from one!
Engine - 1047cc, Air cooled, four stroke, transverse six cylinder. DOHC, 4 valves per cylinder
Bore x Stroke - 64.5 x 53.4 mm
Compression Ratio - 9.3:1
Max Power & Torque-85hp @ 9000 rpm & 52.27 lbs/ft @ 6500 rpm
Dry-Weight - 247 kg
Consumption average - 39 mpg
Top Speed - 218.8 km/h
And then what we have here! First thing is that it is a KAWASAKI. Once you really realize that, you know now what to expect.
If Honda could deliver a CBX, can the Big K be far behind? So it was the Kawasaki Z 1300. It was just not a big-time launch bike, it was the first water-cooled six-cylinder motorcycle with initially with three Mikuni BSW 32-twin carburettors making a whooping 120 hp. It was launched in 1978 at the IFMA show in Cologne. It was probably the first bike whose power was reduced a year later because it has excess of … power and so in 1979, power was bought down to 100hp. This was a big bike, really big, from anyway you look at it, engine, overall size, everything. It made even the CBX1000 look diminutive. And you should listen to its ruff, the CBX seems to have a less intimidating voice in comparison. Listen to the sounds of the K 1300 and CBX 1000.
A smooth engine, adrenaline pumping pick up, even linear flow of power at each band combined with the herculean efforts one need to make it stand on the main stand makes the K 13000 unique. Not to mention the voracious appetite it had. It was more miser than the CBX and would return around 3 miles less than the CBX per gallon. But that was expected. Just like the CBX, when you buy the Z 1300, you know what you are getting into. And you are getting control of one of the most brutal, feared and wanted bikes of not just the 80s, but probably till date. It was boxy to look at, but very you cannot help falling in love with its boxy looks especially once you take it out for a date. And then in the mid 80s, it got fuel injected with a modified suspension and a better transmission. It got more power and it also helped the new owners decrease the visits to the gas station although not by much. Weighing almost 700 pounds, it hardly raised an issue with whom you are travelling. With a 1286 engine, it was good for touring too with oodles of extra baggage. The only thing was the appetite, so all you needed were strategically placed gas stations enroute and the K 1300 would give you the time of your life. Not that it had any shortcomings in the city, after all it was a standard bike, but the size was huge, so it was a little difficult for maneuvering without power.
Yes, Kawasaki has made a name for itself in making the fastest bikes like the H1, K2 750 and the Z900, so it was upto their reputation to keep it. Actually Kawasaki wanted something to beat the CBX, so it made the K 1300 with everything big. It had more power, higher top speed , weighed more, was bigger and costlier but in making everything big, the big Honda got an advantage of easier handling, something very necessary in big bikes. But for what it was/ is, the Kawasaki K 1300 was the uncrowned king of the streets. Work on the K1300 started as early as 1973 and the motto was to bring back the ‘fastest bike’ title to Kawasaki. It was that simple. It was all in the drawing board that the new or future king would have at least a 1200cc engine with 6 cylinders. Work began and later it was found out that due to the sheer mass of the proposed bike, the engine size has to be increased and so it was increased a further 86cc and at the time of launch, they named it as Z 1300. Of course, during the making the sheer, as mentioned even in the CBX case, was a problem and here it was even a bigger engine. The size limits cornering and not to mention the incoming wind thrust. So the option was having a water cooling unit which would also give the provision of diminishing the width in between the cylinders. This would drastically cut the total width of the total engine. Another advantage of water cooling is that it provides good sound insulation and this well-balanced six is notably quiet and smooth with few peers in this respect. And of course, to cut the wind, it could also be fully faired now although that was not selected as an option as it would have taken away the 'street-bike' tag. There was another difficulty and it was in accommodating the customary one carburetor for each cylinder, so the decision was made to use three twin-choke constant-vacuum carburetors which resulted more compact and fitted underneath the fuel tank without impeding the rider. Power is transmitted through a five-speed gearbox to a shaft drive, mounted on the right-hand side of the bike. For a machine of this size with 120 hp, chain drive would not be a good option. And even to stop this machine, 2 disc are just not enough, so it got three with one in the rear.
The bike is capable to a top whack of 135 mph in top gear with a little more to come at the expense of entering the red zone at the rpm meter. The quarter mile is easily achieved in 11 seconds. Very good figures for a non-sports bike. It has a comfortable saddle which means (as mentioned) you can take it for tours. Kawasaki achieved at what it intended to, the fastest bike on the streets or to put it in their way, ‘the king of the streets’.
Engine - 1286cc, Liquid cooled, four stroke, transverse six cylinder, DOHC, 2 valve per cylinder Bore x Stroke - 62 x 71 mm
Compression Ratio - 9.9:1
Max Power & Torque - 120 hp 87.5 kW @ 8000 rpm & 116 Nm @ 6500 rpm
Wet Weight - 296 kg
Consumption average - 36 mpg
Top Speed - 139 mp/h
Before Honda released their first 6 cylinder bike, the 1000cc Honda CBX in 1979 and before Kawasaki released their only 6 cylinder bike, the 1300cc KZ1300, it was BENELLI who had released the world’s first 6 cylinder bike, the BENELLI SEI in the fall of 1972. The move was a direct take on the Japanese invasion from the 60s which annihilated lots of British and Italian companies. Alejandro De Tomaso, the head honcho of Benelli then has come up with this brilliant 750 which he told his engineers to produce a complete new bike unseen and unheard of before and probably not even thought of and not just a bike with 6 cylinders, but one which has to look good, in tune with the times and has to perform. It was no easy task as the Japanese were creating bikes in dozens, all smooth, multi cylinder bikes which were non oil spilling (read easy to maintain) and inexpensive and tell you what! They came with electric starters!
It was not only the Japanese companies that the one time European giants were fighting against, it was also the economic crisis overcome, people were favouring 4 wheelers and if they couldn’t, there was of course the cheaper and better Japanese bikes. Actually the Italian companies were not hit that hard by the invasion like the British or the American companies that were made to close shops, but none the less, Ducati and Guzzi were bought back through government aid. But by the time, the Japanese had made such big strides, that it was impossiblt to compete with them head on. So Benelli wanted to focus and re-strengthen their strength that is through styling and handling.
Benelli had another ace up its sleeve, you see they had a very distinctive racing career. Since 1921, when it had its first motorcycle, Benelli has been winning races more than once can keep track of. This was a genetic factor which De Tomaso wanted to build on maybe exploit and when he bought the company in 1971, he decided Benelli needed a showpiece — a luxury sporting motorcycle and the man himself was a great designer and stylist of sports car and one of his most noted work was the De Tomasa Pantera sports car which had owners like Elvis Pressley.
Although Benelli had a history of in line 4 cylinder bikes, the Sei (of course meaning six in Italian) was different from the other Benellis. Here is an interesting thing. Benelli wanted to take on the Honda. Now the 4 cylinder Honda CB500 had bore and stroke of 56mm x 50.6mm. The Sei had the exact same figure and you just add two more cylinders of the exact same size and there you have it, a 6 cylinder 750cc bike!
If this was coincidental, deliberate or whatever, but this was the subject of controversy as you would expect. And more so, when you know that De Tomaso took over benelli in 1971 and in just 1 year, the Sei was out there for the world, a whole new bike. Many people believe that De Tomaso simply copied the Honda Four and added two cylinders, and rumors persist that parts are interchangeable between the Sei and the Honda! But other sources say that since De Tomaso was already in the automobile business, he knew the most practical things and the said combination was the most efficient anyways you look at it. To say, that the Sei had other similarities with the Honda like single overhead cam run by a chain in the center of the engine, two-piece connecting rods with plain big ends and the Morse Hy-Vo chain primary drive were probably coincidental! The engine was only an inch or so wider than a Honda Four with a gap between each cylinder to pass cooling air. It was fed through graceful manifolds by three Dell’Orto VHB 24mm carburetors. The alternator is on the right side behind the cylinders, with the electric starter tucked in nearby. A kickstarter was provided for macho men or a drained battery.
But that was all where the coincidences ended. Beyond the engine, this was an Italian. This was Benelli. Engines aside, the Sei looked nothing like the Honda. Styled by sports car design house Ghia, the Sei was unmistakably Italian. The cycle parts were Italian designed and built, with a stiff cradle frame that minimized the width of the engine, twin Brembo disc brakes in front, Marzocchi forks and shocks and Borrani aluminum rims.
De Tomaso finally exhibited the Sei at select European shows, but no Sei’s were available for sale for almost two years. A long wait between prototype and production was very typical of Italian manufacturing in the Seventies, but buyers, spoiled by the faster pace of the Japanese factories, became impatient. Finally, there was a test drive carried out by Cycle World in 1974. The ei was compared to a Ferrari V-12, its styling, handling was unmistakably Italian, no vibrations and the deep exhaust note, all in Italian traditions, but for that time, it was exorbitantly priced at $3500. But price was not the only problem, to sale such a priced bike, you need distributors and that too all over the world because limiting it to only a region would not be cost beneficial at all.
All in all, the motorcycle did finally make a presence, albeit not in the scale that De Tomaso had visualized. Benelli sold about 5200 Sei motorcycles between 1974 to 1978 including a recast model in the last year of production. Looking back, the world missed upon a great chance in motorycyling because the Sei was a great motorcycle, looks, riding, handling, everything was Italian or in other words exceptional. The price was an issue and of course being a small company, Benelli didn’t have the market reach like the Japanese, but the present owners of this bike still vouch for the exceptional comfort this gem of a sports tourer offered.
Engine type: 747cc overhead cam, air-cooled inline six
Claimed power: 71hp @ 8,500rpm
Top speed: 126mph
Weight (dry): 220.4kg (485lb)
MPG: 28-35


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