HONDA'S ENDURANCE RACING 1976 - 1980
Content © Joep Kortekaas 2003

mail Joep here if you have questions

Excitement in the pits in the Dutch circuit in the dunes bordering the North Sea - for the first time in 9 years a real Honda factory team had arrived for the 6 hours endurance race.

Honda had retired from GP racing in 1967, and although they had made a brief appearance for the Daytona 1970 200 miles race with the race tuned CB750R, that had not been a real "works" effort, and after winning that race the machines went back to Japan and were not seen again. Then, late 1975, Honda announced that they would be returning to the circuits in 1976, but this time in endurance racing. As it so happened the Dutch 600 km race was the first endurance race that year, and it was there that the Hondas made their first appearance of the season. The effort was run and coordinated by Honda France under management of Jean-Louis Guillou. However, in Zandvoort the team showed up with two machines, riders Leon and Bowler, entered by Honda France, and Stanley Woods and Charlie Williams, entered by Honda UK, an English and a French pit crew and a large number of Japanese technicians and mechanics - a total of 31 people! Hardly any details of the machines were known, and the fact that the mechanics only spoke Japanese and a couple of words French didn't really help things.

The race was won by Christian Leon and J. Bowler, who were much faster than the team Woods/Williams. The latter team also had ignition problems during the race, and, after falling back to 24th position, they retired. This race, however, was a non-championship event.

The 1976 FIM Coupe d'Endurance started with the 1000 km of Mugello, followed by the 24 hours of Barcelona, the 24 hours of Liege in Belgium on the old Francorchamps circuit, the Bol d'Or in Le Mans and the season's closure at the 400 miles of Thruxton.

The supremacy of the Honda RCB racers was so great that all the races were won by them. Christian Leon/Jean-Claude Chemarin won in Mugello, Barcelona was won by Woods/Williams with Leon/Chemarin second, but Leon/Chemarin won Liege.

During training for the Bol d'Or Leon fell off and broke a collarbone, after which Alex George took his place. It made no difference - they won. This win gave Chemarin the European championship title. For Thruxton he teamed with Pat Evans, and came in second behind Christian Huguet and Roger Ruiz on another Honda RCB.

The Machines

The original cylinder head with one ohc had been replaced with one with two overhead camshafts, which ran in plain bearings, and 4 valves per cylinder. Valve sizes: inlet 28 mm, exhaust 24 mm. Valve clearance was set with shims. The camshafts were coupled with gears, but the combination was driven by a duplex chain

The horrible primary drive with two separate chains of the CB750 had been replaced with gears, which also drove the electronic CD magneto ignition, which sat on top of the crankcase, underneath the carburettors. See pic at left. As can also be seen in this picture, the big-end and main bearings were plain bearings, and the driven gear on the primary gearbox shaft contained a shock-absorber. Diameter of the big-end bearings 36 mm, piston pins 17 mm. The pistons had two compression rings and one oil scraper ring. The left crankshaft end still wore the AC generator, but of a much smaller size than the original, and with an output of 150 W.

Carburation was by 4 Kei-hin carburettors of the constant vacuum type with 34 mm diameter (some sources say 32 mm), cast in magnesium and provided with long bellmouths and transparent float bowls. The exhaust system consisted of a 4-into-1 system, that initially gave some problems because it exceeded the allowable noise level. The gearbox was a five-speeder. On the back of the engine was the traditional breather dome, well known from the old GP and production racers. The crankcases were painted black (as were the cylinder block and head) and were said to be cast in an aluminium-magnesium alloy.

There was no electric starter, the bike was kick-started.
The dry-sump lubrication system contained 7 l oil, with an oil cooler under the steering head.

Pics at right show the German bike (originally red parts were painted blue) with the SMAC cast wheels.

< at Left Christian Leon on the RCB .....

picture by Don Morley

At right Jean-Claude Chemarin, Honda's first endurance champion

picture by Terry Howe

The 8 hours race on the Nuerburgring was won by Woods/Williams, this time Leon fell off. At right See pic of Woods.

< At Left .... The 1977 machines .....

For 1977 the bore was increased to 70 mm, bringing the total capacity to 997.5 cc. Carburettor diameter 35 mm. Claimed power rose to 125 bhp at 9,000 rpm, and the top speed was over 270 km/h. The AC generator disappeared from the crankshaft and was placed on top of the crankcase, together with the ignition magneto.

Many teams riding the '76 RCBs updated their machines in accordance with the '77 specifications. It appeared that a set of 35 mm Kei-hin carbs cost some US$ 6,800..yes, six thousand eight hundred! And we're talking 1977! The exhaust system was changed from 4-into-1 to 4-into-2-into-1. There was also a new, lighter frame, constructed in Reynolds 531 tubing, and through the extensive use of titanium and electron the total dry weight was reduced to just under 170 kg. The oil cooler moved into the nose of the fairing ........ (see pic at right).

Some teams, using the '76 RCBs, used frames built by Dutch frame specialist Nico Bakker - see pic at left, some with excellent results, although at least one team, notably the Dutch, preferred the original Honda frame.

As had happened before, Honda reduced their works effort for the 1978 endurance season, and there was only one real works RCB for Leon and Chemarin, and one semi-works bike for Woods and Williams. Notwithstanding that, the Honda dominance was again total.

The 1000 km of Misano, on the "Autodromo Santamonica", was won by Leon/Chemarin, followed by Green/Williams, also RCB mounted, and the 8 hours of the Nuerburgring was again for Leon/Chemarin followed by Green/Williams and Daehne/Schwemmer on RCBs. > See pic at right of Leon/Williams

Since the new 1978 RCB had been giving problems in Zandvoort, the following three races in Liege, Misano and the Nuerburgring had been contested with the '77 model, but for the 24 hours race of Barcelona the 1978 RCB was used. While leading the race, Chemarin was hit by Palomo, who piloted a Ducati with Grau, and both riders fell off. Both machines were lightly damaged, but it took the Honda crew only tenminutes to get the bike going again, minus its fairing. Because of the delay, Leon/Chemarin were now in fifth position, but six hours later they were back leading the race, which they won with a new record number of laps. Second were Williams/Woods, third Luc/Buytaert, all RCB mounted.

The Last race of the season was the 1000 km of Brands Hatch, which was won by Woods/Williams, with Leon/Chemarin second and Green/Murray fifth on RCBs. The European championship was again won by Christian Leon and Jean-Claude Chemarin (see pic at left of Christian Leon and Jean-Claude Chemarin), third was Charlie Williams Honda RCB), fourth Jacques Luc (Honda RCB), fifth Gary Green (Honda RCB) and sixth Roger Ruiz (National Moto) and Stan Woods (Honda RCB).

The 8 hours of the Nuerburgring again saw Leon/Chemarin as the winners. How professional the teamwork had become is shown by the time of the pit stops: 8.2 seconds to tank, top-up the oil and change riders. see pic at right. Second place was for Daehne/Schwemmer on an RCB.

The 1979 Bikes

For the Bol d'Or, a second works Honda was brought into action with riders Hatton and Blake, entered by the Australian importer (see pic at left). This bike had a bore and stroke of 70 x 69 mm, giving a total capacity of 1062 cc. Leon and Chemarin's Honda's bore was enlarged from 70 to 73 mm at the same stroke of 64.8 mm, giving a capacity of 1084.9 cc. Both bike were clocked at 263 km/h on the straight. The weight was given as 160 kg, but during scruteneering the actual weight on the scales was 200 kg.

Honda announced that they would compete with two machines, which were based on the CB900F, and were no longer called RCB 1000 but RSC 1000. Which is interesting: the CB900F was developed based on the RCB - and now the new RSC racer was based on the CB900F!

The next race, the 8 hours of Assen, was again for Fontan/Moineau, this time with Leon/Chemarin in second position.

Because of heavy mist, the 24 hours of Liege became 20.5 hours, and was won by Fontan/Moineau on the RSC (see pic at left of Fontan/Moineau).

The 1980 Machine

As already mentioned, the 1980 RSC racers were no longer based on the CB750 engine, but on the CB900F "Bol d'Or" (see pics at right). The 1980 FIM rules and regulations stipulated a.o. that cylinder head and crankcase castings should be equal to the ones used in the production machines, and the RCB engines based on the CB750 simply didn't comply. Bore and stroke were 70 x 69 mm for a total capacity of 1062 cc. Compression ratio 10.5 : 1. Claimed power output was still 135 bhp at 10,000 rpm. Inlet valve diameter 26 mm, exhaust valve diameter 22.5 mm. Carburettors Kei-hin VB 51 A - 32 mm CV (according the FIM rules, standard carbs had to be used). The ignition and AC generator were situated on the crankshaft ends, asin the production models, and the engines used the Morse chain camshaft drive and primary drive (albeit with a wider chain) of the production models. Contrary to the standard CB900F, the RSC had dry-sump lubrication with a double trochoid oil pump left on the gearbox. The frames were similar to the ones used in 1979.