WB. Inflation

Posted Feb. 29, 2016

This story was prompted by an article on the new 2016 Ducati 959 Panigale in Roadracing World magazine. They referred to the 955cc motorcycle as a “middle-weight” sportbike. When did a 955cc motorcycle become considered middle-weight?

Back when I became interested in motorcycles, in the mid-1960s, there were a relatively common set of standard sizes for motors in Japan and Europe. The U.S. had a couple of conventional displacements as well. The European sizes followed, mostly, the FIM Gran Prix racing classes. There were a couple of small bike sizes, 50cc and 80cc, then 125cc. The next steps up were to the more serious classes: 250cc, 350cc, and 500cc. The 500cc class was the biggest motor size allowed in FIM Gran Prix racing for many years.

In the U.S. racing scene the AMA set the limit for OHV and OHC machines (mostly British singles and twins) to 500cc and side-valve motors (Harley Davidson’s KR750) to 750cc.

Most of the Gran Prix bikes were factory specials, just like with MotoGP today, so there was no rule that required the various manufacturers to stick to these sizes when they built their mass production bikes, but they mostly did. There was some fudging around with the numbers. For example, Honda’s Hawk and Super Hawk twins of the late 1960s were 250cc and 305cc, respectively. Although 305cc was an odd displacement, we all considered it a 350cc class bike. It was replaced by the CB350, which in spite of its name was actually 321cc.

Street bikes didn’t stop at 500cc like the GP bikes did. There was a 650cc/750cc class with bikes like the Triumph 650cc Bonneville and Norton 750 Commando. Honda built a 450cc twin for the 500cc class, then in 1969 it finally pulled the pin and tossed the CB750 4-cylnder grenade, er, I mean motorcycle, into the market.

In 1970 there was an over-750cc class but it was very sparcely populated. Harley-Davidson had the 883cc Sportster and a couple of 1,200cc long-haul bikes like the Electra Glide. The German maker Munch built a Mammut 1200 by shoe-horning an NSU 1,147cc car engine into a two-wheel chassis.

At the beginning of the decade the major manufacturers made bikes mostly within these classes. I won’t list then all, but BMW had 500cc, 600cc and 750cc models; Ducati built 250cc, 350cc and 450cc singles, Honda had 125cc, 250cc, 350cc, 450cc and the aforementioned 750cc motorcycle in their lineup. Kawasaki had the 250cc Samauri, the 338cc Avenger, and the 500cc H1; Suzuki’s street bike lineup included a 250cc and 500cc models. Moto Guzzi and Norton both had 750cc bikes; Triumph had a 250cc single, a 500cc twin, and a 750cc triple along with its 650cc twins; Yamaha had the 250cc DS-6 and the 350cc R5.

In 1971 Ducati released its first big bike, a 750cc twin, actual displacement 748ccs.. Kawasaki dropped the 903cc Z1 into the market, joining Laverda in making bikes in the Open class. If you look at the street motorcycles in 1972 nearly every manufacture offered bikes in one of these “standard” classes: 125cc, 250cc, 350cc, 500cc, 650/750cc, and above 750cc.

Bonneville_T120 inflationBonneville inflation. Left is the original 650cc, right is the 2016 model. To get from A to B the Bonneville went from 650cc to 760cc then 865cc and now 1,200ccs

Then things started changing. Ducati’s bevel twin 750 grew to 864ccs in 1975, then became 973ccs in the Mille models right at the end of its run. The Yamaha RD350 became an RD400. Honda’s 500 four became 550. The Norton 750 Commando grew to 850cc, and Moto Guzzi’s 750 S3 became the 850 LeMans. Honda replaced its CB350F with a CB400F, which was actually 408cc. Kawasaki’s mighty 900cc Z1 was replaced with the KZ1000, with an actual displacement of 1,015cc. The iconic Triumph Bonneville of the 1970s was a 650cc parallel twin. The newer Bonneville debuted in 2001 with a 790cc motor, which grew to 865cc and this year the T120 Bonnie has 1,200cc.

Honda’s GL1000 Gold Wing started with 4 cylinders and a 999cc displacement but somewhere it gained two more cylinders and became the GL1800 with 1,832 cubic centimeters. The ST1100 with 1085ccs became the ST1300 with actual displacement of 1,261ccs.

Inflation of the CB350. L to R is the original CB350, the CB360, and the CB400T.

It wasn’t just the big bikes either. Honda’s popular CB350, with an actual displacement of 321cc, (yes, I had one) became a CB360 (356cc), then a CB400T (395cc displacement). Even at the small end this is still going on. For years Kawasaki offered a 250cc Ninja, a very popular “first sport bike.” Now it’s the 300 Ninja. Honda’s CBR250R grew to the CBR300T. Then KTM one-upped them all with the 390cc Duke.

Why all this creeping up? Manufacturers claimed new noise and emissions rulings were robbing power from the bikes and make their motors bigger to compensate. And in America, bigger is better, right?

So what is a “middleweight” now and what was it then? What bike was considered the ideal learner’s bike? Back in my learning days a middleweight was a 350cc-400cc bike. Today it’s, what, a 750cc bike, or even Ducati’s 959 Panigale? Good grief! In the 1990s Ducati was winning World Superbike Championships with smaller motors than the 956cc of the 959 Panigale. It wasn’t that long ago.

Good learner bikes were the Honda CB160/175, or the Yamaha RD125. Today it seems a good learner’s bike is something around 300cc, although some people would go up to 500cc and still consider it a learner’s bike. Can you even buy a 125cc street bike these days?

Where will it end? For a short time 1,400ccs seemed the top displacement, excepting the Gold Wing GL1800. Kawasaki Concours 14, Suzuki Hayabusa (started with a 1,299cc motor now has been inflated to 1,340ccs). Then, just after the turn of the century Yamaha launched a 1,670cc Road Star Warrior and Honda had the VTX1800. Triumph upped the ante with the 2,294cc Rocket three. Sheesh! There are a lot of small cars with smaller motors.

It will be interesting to watch the manufactures in the coming years to see what they do with engine displacement.

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