On a couple of occasions, I’ve had the opportunity to be present when one of the fabled six-cylinder Honda 250s was dismantled. So I have some familiarity with the way those engines were constructed. At the time, they represented the very highest technology that the Honda Motor Company had created.
Although people in the automotive racing world had decided two valves per cylinder gave optimum flow, Honda realized there was another reason to use four small valves. They could reach higher rpm than two larger valves could manage because the lightweight, little valves could follow the camshaft contour with a reasonably sized spring.
Here, with this CBR600RR engine, we have four valves per cylinder. The Honda inline-six, turning 18,000 peak rpm, also had four valves per cylinder. They were really tiny valves; talk about assembling parts with tweezers. The ultra-high-rpm six also had an oil gallery that ran directly across the engine right underneath its crankshaft.
In the case of the six, the crankshaft was built up from many pieces pressed together and with rolling bearings. This engine uses a one-piece forged crankshaft, which is much cheaper. If you had to make a replacement crankshaft today for a Honda six, it would cost, well, you wouldn’t get much change from a hundred grand.
This crankshaft is available down at the Honda dealer at the bottom of the road. You might have to wait a couple of days for rush shipment, but it is available for sale to the public. Racing versions of this production 600 have revved as high as 17,000 rpm, possibly even as high as 18,000 rpm.
What was happening in the 1960s as the leading edge of design has now become normal technology for production. What was 100-percent unobtanium in 1966 has become a consumer product today. This is the nature of technology. First we have to learn how to do it, and then we can engineer ways, we hope, everyone can do it.