To fully understand the importance of what is called "the Honda 6" in the history of motorcycling, leading to the RC 174, we can obviously place it on a technological level, but also insert it into the saga of the duel between the International Motorcycling Federation and the builders, a worthy parallel to that of the police and the robbers!
Find here the introduction to this short story of the very famous RC 174 also called Honda 6.
This series of articles is inspired by the announced presence of the most authentic replica of la HondaRC174 during the Sunday Ride Classic on the Paul Ricard circuit, May 17 & 18, 2025...
4/ The RC174
At the start of 1967, in the 250cc category, it was decided not to change a winning team and Honda once again lined up the legendary Mike Hailwood/RC166 pairing alongside Ralph Bryans.
At the same time, Honda also launched a new offensive in the 350cc class, where until now the machines with the golden wing had been roughly underbored 500cc 4-cylinders. This was no longer enough to counter Giacomo Agostini's MV Agusta, and Mike Hailwood complained about the handling and maneuverability of the four-cylinders, praising instead the behavior of the "little" Honda 6.
Honda therefore decided to build an entirely new machine to replace the 173-cylinder RC4, a 297,06 cc version of its RC166 engine with a new 41 mm bore and 37,5 mm stroke. The chassis was stiffer and more compact than the 250 cc, the front brakes resized, the engine better cooled with its narrower fork. Called the RC174, it developed 66 horsepower at 17 rpm. It was fitted with Ø000 or 22 mm carburetors.
It was a complete success, as Mike Hailwood won the title by winning the first five races, and Ralph Bryans collected enough points to finish third in the world championship behind Giacomo Agostini!
A second legendary "Honda 6" in its category was born and it is, down to the smallest details, a copy of this motorcycle, by far the most faithful of copies, that you will see at the Sunday Ride Classic.
In 250cc, the Yamahas have increased their power and, being lighter than the 4-strokes, give the latter a hard time on fast circuits like Francorchamps and Monza.
Honda therefore decided at the end of the season, on its new successful RC174 engine, to reduce the stroke to 31.50mm, while retaining the Ø41mm bore. The RC166 became the RC166B with a power output of 59 hp. Even with this slight increase in power, it would take all of Mike Hailwood's talent to compete with Phil Read, with both men finishing the season with exactly the same number of points! The Honda rider nevertheless won the title, as he had 5 wins against Phil Read's 4.
Honda will offer its riders a final version of the 350, the RC174B with internal modifications to the engine, and more visible ones like Ø24mm carburetors.
At the very end of the season, in both 250cc and 350cc, Honda will make available versions of its 6-cylinder frames with the engine tilted to the front.
To be continued…
This series of articles is inspired by the announced presence of the most authentic replica of la HondaRC174 during the Sunday Ride Classic on the Paul Ricard circuit, May 17 & 18, 2025...
Photo credit: Honda
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