Honda 900 Bol d’Or
BARN TO TRY
While Honda initiated the revolution that saw the four-cylinder motorcycle take over the world, by the mid-70s its single-overhead camshaft CB750 was no longer king.
In 1972 Kawasaki’s Z1 took over from Honda’s CB750 and Suzuki and Yamaha soon had double-overhead camshaft fours. But these were all two-valve cylinder head designs and Honda, more than anyone, appreciated the advantage of four valves per cylinder.
During the 1960s, Honda’s four-valve-per-cylinder machines completely dominated Grand Prix racing and the four-valve RCB endurance racers continued this supremacy into the late 1970s. It was only a matter of time before a four-valve cylinder head appeared on a Honda production bike.
Honda’s first four-valve production engine was the spectacular six-cylinder CBX, but this was never going to be a volume seller. So for 1979 a new double-overhead camshaft four-cylinder 900 replaced the single-overhead camshaft CB750.
Although the 900 capitalised on the success of the RCB in endurance racing, and was called the Bol d’Or, there was very little in common between the CB750-based RCB and the new engine. The new 900 four represented a change in direction from the previous evolutionary program, sharing many design characteristics with the CBX1000.
In addition to double-overhead camshafts and four valves per cylinder, the primary drive was by Hy-Vo chain to a jackshaft that drove the clutch and spring-loaded damper. The alternator was on the right end of the five-bearing forged crankshaft, with electronic ignition on the left.
There were two cam chains, with a Hy-Vo chain connecting the crank with the exhaust camshaft, and a shorter chain driving the intake camshaft from the exhaust one. Valve clearance adjustment was by shim on top of the cam followers.
The cylinder head featured a relatively wide (for a four-valver) 63-degree valve angle. This design was arguably obsolete by 1979, as it was inherited from the 1960s Honda racers and not the more recent Cosworth narrow-angle automotive designs.
The 902cc CB900FZ (64.5x69mm) featured a low compression ratio of 8.8:1, four 32mm Keihin CV carburettors and an oil cooler fitted to the front downtubes.
It delivered 95hp at 9000rpm – a ballpark figure for 900 fours at the time. The question everyone asked was why was it only 900cc when Suzuki, Kawasaki, and Yamaha had full litre fours.
FAST BUT BLAND
There was little exceptional about the chassis: the double-cradle steel frame included removable right-side rails to simplify engine work but with more gusseting around the steering head than earlier 750s.
Handling weaknesses included nylon swingarm bushes, a front fork with skinny 35mm tubes and adjustable FVQ (Fade Very Quickly) shocks. Braking was by a pair of twin 280mm front discs while the front and rear wheels were 19- and 18-inch composite aluminium Comstar items respectively.
While not especially light (the CB900F weighed 233kg), the performance of the new four was impressive. The top speed was around 210km/h but without the individual personality of its CB750 predecessor the CB900F was considered a little bland.
For many, however, the CB900F was the perfect ‘Universal Japanese Motorcycle’ (UJM), the ubiquitous, Japanese, across-the-frame four. Although blighted by the perennial Honda cam chain problem, these were steady, undistinguished motorcycles that improved gradually every year. Updates for 1980 saw needle roller swingarm bearings and an air-assisted front fork. Further improvements for the 1981 CB900FB (pictured here) included a larger-diameter fork (37mm) and dual-piston brake calipers from the racing CB1100R.
Among the other 31 improvements for ’81 were a stronger cam chain tensioner and different valves. Also available was the CB900F2B with a 16-piece, three-quarter fairing and leg shields, housing a clock and voltmeter. Although the CB900F lasted until 1983, by then it had been overtaken by the CB1100F.
Where the CB900F excelled was as an everyday riding machine. Motorcycles were less specialised in the early 1980s and the Bol d’Or was forgiving, working well as a high-speed sportster, yet delivering the goods in the city or as a tourer.
The suspension and riding position provided a perfect compromise between sports riding and comfort. Factor in exceptional finish and reliability, all for around three grand, and you can see why the Bol d’Or was a success. It may have been bland but, as a representative of the era of the universal motorcycle, the Bol d’Or was one of the best.
THE VALUE PROPOSITION:
– New (1981) $3226
– Good condition $4000
– Mint condition $8000
WANT TO KNOW MORE?
Get this book The Honda Story:
Believe it or not, there is a Bol d’Or website based in Holland.
And another in France