Shoichiro Irimajiri (above), a brilliant engineer who worked on Honda's GP racing bikes of the 1960s, was also the man responsible for the mighty CBX1000
The Honda CBX1000, with its six-cylinder engine, remains one of our most favourite motorcycles from the 1970s/80s. The Honda CBX was in production from 1978 to 1982 and a total of only 40,000 units were ever produced. Weighing in at 247 kilos dry and with 103 horsepower from its DOHC, 24-valve, 1047cc air-cooled inline-six (fuelled by all of six carburetors…), the CBX could blast through the quarter-mile in 11.36 seconds and hit a top speed of 225km/h. But the CBX was special way beyond its numbers – the visual spectacle, the sheer drama of the super-smooth, high-revving six-cylinder engine… it was, and remains, an incomparable motorcycle.
We are big fans of the CBX and keep scouring the Web for pictures of the bike. During one such recent hunt, we came across two letters written by Shoichiro Irimajiri, the man responsible for engineering and developing the CBX. As a young engineer, Irimajiri started working for Honda in the early-1960s and worked on Honda’s GP racing bikes of that era, some of which were pretty amazing. Irimajiri was, in fact, responsible for designing the engines of the 1965 RC147 and RC165. The RC147 had a five-cylinder 125cc engine that produced 32bhp and revved to 19,500rpm, while the RC165 had a 250cc six-cylinder engine that made 52bhp and revved to 14,500rpm.
But coming back to Irimajiri’s letters, which we mentioned earlier, the first has been written in February 1987 and is addressed to Clint Hooper, then National Director of the International CBX Owners Association (ICOA). And the second has been written in August 1990 and was sent to Mike Brown, then Mid-Atlantic Director, ICOA. Here, we present some excerpts from the two letters – we’re sure CBX owners and fans will be interested in reading what Irimajiri had to say about the CBX:
“I really enjoyed the time I spent involved with the development of the CBX, especially the design. It was a big surprise and honour to find that there are still so many people who love the CBX.”
“We started developing the CBX in around 1976. The biggest problem with the CBX was the weight. In order to guarantee sufficient horsepower, the weight had climbed to over 200kg and how to get it down was our biggest headache.”
“While we were working on the CBX, for comparison purposes we also built the CB1000F, which has an air-cooled DOHC four-cylinder engine. This motorcycle was based on the CBR1000, an endurance racer and so it was extremely light and actually much faster than the CBX. But, nevertheless, we felt there was something exhilarating and exciting about the six-cylinder CBX that was lacking in the four-cylinder CB1000F. The deep rumble of the exhaust, the feeling of acceleration, the vibration, its smooth high rev engine – something in the CBX that could not be measured in numbers like speed and weight made it a very sexy machine.”
“There was a big discussion among the project team about which motorcycle we should go with, and for our plan to develop a totally new ‘superbike’ unlike any that had been made before, we chose, not an improved model of the CBR1000, but the layout of the six-cylinder CBX.”
“If I had it to do over again, I think now I would design the CBX with a water-cooled engine. It would be lighter and would probably put out about 130 horsepower.”
Well, we really do wish Shoichiro Irimajiri was still around at Honda, so he could have a go at building a modern-day CBX. But while that isn’t happening anytime soon, for those who may be interested in reading more about Irimajiri and the CBX, you should definitely go here.
Source: West Coast CBX