Cycle News - Archive Issues - 1970's

T he World Championship winning RC·450-79 is overkill at the limit. That Graham Noyce or anyone else could race such a bike and win a World Championship makes me applaud their skill. That Graham had even tried to race a larger 493cc version a t the beginning of the series would have had me applying fQr Blue Cross and finding religion. The bike I was trying to ride was Jimmy Ellis' factory RC-450- 79 to gain an impression for this article of the similar motocrosser which had taken Noyce to his 1979 FIM 500cc World Championship. Disappointingly, Ellis' bike and the RC-450s of the other American Team Honda nders were completely different in the suspension department from the factory stocker Noyce was riding. The modifications were an attempt to improve the suspension design of Honda's Open class bike which in factory form had remained stagnant since the beginning of 1978 when the RC-450 was introduced. At that time the new increased displacement 450cc Honda came with reduced II-inch travel suspension. Only the year before, 1977, Team Honda's Marty Smith had won the National Championship with the RC400-77. This was probably the finest works Honda ever built, and with its much easier to control 400cc engine and longer 12-inch travel Showa forks/Fox AirShox suspension it couldn't be faulted. I rode that bike and fell in love. When the RC-450-78 appeared, it seemed Honda had taken a step backward in building a bike with less suspension travel, more power than, needed, and less rear braking control with the switch from a full-floating to non-floating rear brake. The new RC-450 hardly proved to be a resounding success, particularly in America during the 1978 season, but Brad Lackey did take it to third place in the 500cc World Championship MX Series with'a few Grand Prix victories thrown in. And now in unchanged form for the 1979 season, it was the bike that gave Honda and Graham Noyce their first-ever World Championship MX win. It should be remembered though, that the other top riders like Mikkola and DeCoster were out of action for the first races of the series with injuries, and then throughout the series Mikkola, DeCoster and Lackey were hampered with mechanical breakdowns. Noyce cruised along on the ultra reliable RC450 and compiled a perfect finishing record thanks to mechanic Bill Buchka. Noyce kept his Honda in stock condition throughout the Championship with II inches of travel. The front forks were 39mm factory Showa units which use no air, just internal coil springs for suspension. At the rear is a massive Honda aluminum swingarm which places the shocks at a fairly . radical 30-degree laydown position relative to the swingarm. The bike came equipped with Showa deCarbon piggyback reservoir shocks, but Noyce had replaced them with the excellent Ohlins deCarbon piggyback reservoir shocks which are easier to keep dialedin thanks to the presence of a service' representative from Ohlins at each Grand Prix. Jimmy Ellis' RC-450. on the otherhand, had its suspension completely changed. Up' front were the aftermarket. variety KYB front forks with II inches of travel. These forks feature a lot of trick machine work on the lower sliders, but when it comes to performance they aren't much better than the garden variety Kayabas which come stock and Yamaha YZs and Suzuki RMs. At the rear. Ellis was also using the Ohlins _ piggyback shocks of 15\-2-inch length, (Topl Graham Noyce on the basically-stock RC-450 at the USGP. (AboveI Ellis added a full·floating brake and banana swingarm. (Belowl A 38mm Keihin carb and six-petal reed valve feed the monster 450cc engine. (Bottoml The author braves a few laps on one potent MXer. but hooked up to an American Honda built steel banana style swingarm. This swingarm 'locates the shock in a more perpendicular 60·degree angle for II ~ inches of rear wheel travel. The idea in mounting the shock more upright is to gain a more constant leverage ratio on the shock throughout rear wheel travel. That way damping stays consistent throughout rear wheel travel, and spring rates would be easier to dial-in. The radical 30-degree laydown shock position on Noyce's bike means damping will be stiffer and react less for smaller bumps when the suspension is extended something you don't want - then damping becomes lighter as travel is used .up and the leverage ratio on the shock decreases. All this sounds great in theory, having softer damping for full extension and then firmer damping as the suspension bottoms out, but it doesn't always work that well on the motocross track. You may want less damping in your shocks, particularly less rebound damping, as the suspension bottoms out so it can react quicker to extend again before the next bump hits it and bottoms it out even worse. Presently most motocross shocks are speed sensitive in their damping action which turns out to be pretty good for most racing applications. Damping action varies according to impact compression and spring rebound force. There are times when we might want a. shock with position sensitive damping as well. Curnutt makes such a shock. But for the time being there is no shock available which is both position and speed sensitive in its damping. We're still waiting for the perfect motocross shock. As far as spring rates go. I don't think it matters too much what angle the shock is positioned in. What with shocks that have double and triple rate springs, straight wound and progressive, there should be no problem adjusting the springs to suit the rear suspension. And then there is the Fox dual air spring AirShox which can easily be dialed-in to meet the required progressive spring rates for any design of rear suspension. Back to the testing. After scaring myself silly with the third gear acceleration of Ellis' RC-450. I took the bike around the rest of the test course, Sunshine Motocross Speedway in St. Petersburg. Florida. But no sooner did I hit a section of rough sand whoops and the bike started kicking like a runaway pogo stick, trying to throw me into wild tank slappers. The front forks were softer than mush while the rear end kicked like a mule. I tried a cou pIe of times to go faster to smooth things out. but I just got more out of shape and with that much power at my disposal I knew I would just get into trouble sooner or later. I brought the bike into the pits and parked it. Jimmy Ellis' tuner and father, George Ellis, explained to me that was how Jimmy liked the bike set up. That it was difficult to ride slow. but once up to competitive speed it would handle batter. The only trouble is I don't ride as fast as Jimmy Ellis. And I have ridden enough factory bikes to know the others all handled well at the speeds I was accustomed to going. Given the opportunity to adjust the suspension for myself I most certainly could have made the bike rideable, but even then I don't know how well it could be improve-d without major suspension revisions. And if the bike handled as well as claimed when pushed to its limit. it certainly couldn't be very manageable when slowing down for corners or bouncing through turns. That everyone of the American Team Honda riders have set their bikes up with different suspensions and were constantly changing them throughout the 1979 Nationals seems to indicate none of them were very happy with how the bikes handled. Graham Noyce. on the other hand. left well enough alone, compensated for any idiosyncrasies and went out and won on the bike. In either case. we are probably seeing the last of the RC-450 Honda's perplexing suspension, if not the monstrous motor. • o ~ 1-0 (l) ..0 o .... u o 19

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