Suzuki Introduces New Single-Shock Works Motocrosser
SUZUKI INTRODUCES NEW SINGLE-SHOCK WORKS MOTOCROSSER
Team Suzuki has now joined the other three major Japanese factory motocross teams with the introduction of their own single rear shock works bikes. With the Full Floating Suspension System, the new bikes were first seen in Europe earlier this season at the 250cc and 500cc World Championships. Their introduction at American races was delayed a number of months, possibly because Suzuki felt their being seen would affect the sales of conventional twin shock RM production motocrossers. Yamaha pioneered monoshock design in 1973 and won the 250cc World Championship with it that year, offering production Monocross YZs the following season, and Kawasaki followed with the Uni-Trak design introduced in 1979, and put into 1980 production. The Uni-Trak system incorporates variable leverage ratio (VLR) suspension on the factory KX bikes.
Strangely enough, Suzuki’s older works twin shock works bikes were so refined they were possibly the most competitive of all the factory bikes. In fact, team rider Kent Howerton used a twin shock RH to sweep the first three races of this year’s 250cc National Championship. But, in the words of Team Suzuki manager Mark Blackwell, the new “Floater bikes” were being tried because, “The current twin shock rear suspension system is developed fully to its optimum and really does work well, but development needs to continue with newer ideas.”
The new Floater Suzukis were brought to their first American race showing at the High-Point National in West Virginia, the fourth race of the 1980 season’s 250cc Nationals and the first round for the 500cc class. In what proved to be an exciting debut for the new bikes, Kent Howerton rode his RH 250-80 Floater to his fourth straight National win in the 250cc class. Luck in the 500cc class proved to be just the opposite as Suzuki’s reigning Open class Champion Danny LaPorte suffered a broken front axle which caused the bike to pitch him over the handlebars one moto,
then he and teammate Marty Smith were put out of contention in the other motos as well when they were both involved in first turn pileups after the starts. Suzuki is employing its Floating Sus pension System on both its RH 250-80 and RN 440-80 works motocrossers. The monoshock design is very similar to Ka wasaki's Uni-Trak system. The difference is that the Suzuki's deCarbon reservoir Kayaba coil-over shock assembly is lo cated in an inverted position (like Honda's Pro-Link system) for easy adjustment of spring preload, and the shock's pivoting rocker arm assembly is similar to a swing arm in that it is the same width as the frame and pivots on a swing arm-type bolt with needle-bearing frame inserts.
The advantages of a monoshock rear suspension system like Suzuki’s Floating Suspension System are many. A single rear shock assembly positioned low in the frame right behind the engine helps lower the bike’s center of gravity and move its mass closer to the center as well, improving handling and response. The main advantage, though, is that the shock assembly’s changing rocker arm geometry during rear wheel travel provides a variable leverage ratio (VLR) rear suspension. This translates into softer spring and damping rates when the rear suspension is extended (perfect for small bumps likely to be encountered when the suspension is extended) and then becoming progressively firmer as the suspension compresses towards bottoming out (caused by large bumps or landing off jumps). This change in suspension rate can be as much as 40 or 50 percent in a VLR design-, while for comparison a motocross bike with conventional twin shock laydown rear suspension can’t provide more than a 20 percent change.
Rear wheel travel on the Suzuki Floaters is 11.8 in. with adjustment of the swing arm lever arm length allowing some change in both rear wheel travel and ride height. Up front, huge new 43mm o.d. Kayaba air/spring forks offer an equal
amount of travel with no Hex.
The engines are new as well this year. Both the RH 250-80 and RN 440-80 have cylinder reed induction, unlike their production RM counterparts which use case reed induction, and the magnesium engine cases are redesigned to allow additional clearance for the shock assembly now positioned behind them. As always the cylinders use steel liners, but now the intake system employs a huge bridged cylinder window and feed passages from the intake track to the crankcase and side transfer ports. The cylinder reed assembly is a V-block with four metal reeds per side. Both models run five-speed transmissions. Carburetion is by 38mm round slide Mikuni with magnesium body, though Kent Howerton has been using a new guillotine flat side Mikuni on his 250cc bike which he claims helps smooth out the powerband.
Weight for both bikes is right on the FI M’s new raised minimum weight limits of 209 lb. for the RH 250-80 and 224 lb. for the RN 440-80.—Jim Gianatsis a
