Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126452
o 00 0') The Pro-Unk model at Anaheim featured Showa air/spring front forks and a Showa coil-over decarbon monoahock with remote reservoir, The shock's rocker arm is atteched by edjuateble IInkege to the frame, 10 off an eighth place finish in what was his first race for the red marque. Called the Pro-Link., Honda's new RC works bike rear suspension is, indeed, very similar to Kawasaki's UniTrak rear suspension system, but with some very important differences. Once again Honda has proven that when they put their mind to doing something, they usually do it better than anything that has been done before. The whole idea of the Pro- Link, li-ke Uni- Trak, is variable leverage ratio suspension, VLRS uses changing geometry in the rear suspension components to allow the shock absorber/spring assembly to work less when the rear suspension is in the area of full extension and to work more when the rear suspension travels towards full compression. The operational result with VLRS is a very soft rea"r suspension when extended to offer good wheel control over small bumps like those down a straightaway or chatter bumps encountered while braking into corners. However, compression of the rear suspension, such as off jumps or through deep whoops, reduces leverage on the shock/spring assembly to increase damping and spring rate to meet additional loading force. The Pro-Link accomplishes the same variable leverage ratio idea as the VLRS swingarm which Honda introduced on its RC 400 works bikes in the 1979 Trans-USA Series, The VLRS swingarm assembly is a good idea in that it uses conventional shock absorbers while the complete VLRS swingarm assembly can be adapted easily to fit almost any conventional motocross bike frame. But the Pro-Link offers even additional advantages over the VLRS swingarm assembly like less working parts and less unsprung weight, That translates to a smoother rear suspension with quicker response. There are also two nice advantages in locating the Pro-Link's attachment points and shock assembly close to the engine and the middle of the bike's chassis. The first is that by moving the bike's mass or weight closer to the center of gravity, the bike itself becomes much more responsive in its handling. Directional changes, like in corners or over jumps, become much easier, The othei' advantage in locating the rear suspension's input forces so close to the center of gravity is improved weight transfer under acceleration and braking. There is more force available to load the front and rear wheels under braking and acceleration to improve traction. Honda's Pro-Link even offers a few design improvements over Kawasaki's Uni-Trak. Hond~'s leverage rocker arm system is lighter, sturdier and better protected than Kawasaki's. Spring preload, ride height and travel adjustment are quickly and easily adjusted on the Honda from outside the bike. The Kawasaki requires partial ~bly to make th~ minor adjustments. Just as interesting as the new rear suspension is the water-cooled 250cc powerpla1?t which is not a bolt-up kit, but required an entire new engine design to accommodate. The complete cooling system almost defies description, with its crankshaft driven twin waterpumps which circulate coolant through the head and cylinder assem· bly twice amid a tangle of hoses and cast magnesium pipes reminiscent of the octopus-like mini creature in Alien. The ducted radiator and gas tank assembly add to the Nostromolike setting. Why Honda opted for such a complex water-cooling system or any water-cooling system at all will have to remain a mystery for the time being. It certainly isn't of any benefit in short mota Supercross events. For longer 45minute mota outdoor events, the water-cooling of 250cc motocrossers remains a questionable benefit as well, since the last few years have seen manufacturers shifting away from ultra-powerful.and peaky powerbands which might require coolmg to help keep the horsepower ratings up, to broader and more tractable powerbands where a faded pony or two at peak rpm might never be mis8oed. The less power an engine has the less heat it builds up, anyway. Husqvarna won the 1979 250cc World Championship with a production derived engine producing less horsepower than what any of the Japan~ big four offer with their production bikes. Weight certainly isn't a factor against water-cooling t~ days as the FlM's minimum weight limit is easily within reach of any company with magnesium and titanium at their disposal. Suzuki proved during 1979 they 'could build a RA 125 watercooled works bike which was lighter than their RA 125 aircooled version. So there you have it. Honda's ProLink is quite an amazing piece of machinery, certainly the most innovative MX package we've seen since, perhaps, the introduction of the Yamaha Monocross in 1973. With the AMA's removal of the claiming rule from the books we can expect to see a lot of exciting MX machinery coming our way very soon. •