Cycle News - Archive Issues - 1970's

low left) Transfer ports are mild. but one ride will convince you there's no need sembly and gearbox. (Below rightl The mighty MC..ao at rest, Specifications Olsplac:ement..••..•••..' , ................•.......... 419.8cc ~n;tn)ke ..............•......•................... 86nnmf74nnm Ignition Internal rotor Motoplat COl Carburetor. . .. . ..•..•................................ 40mm Bing Transmission Five-speed. with primary kick start Front suspension ............•.. Manocchi air/oil forks. 10.8 in. travel Rear suspension Ohlins gas/oil shocks. 11.8 in. travel Front tire , , .. , . . . . .. 3.00 x 21 Metzeler Rear tire 4.50 x 1B Metzeler Chain size 530 seat height , ,., ,. 35.8 in. Ground clearance : , ..•....... , 11.6 in. Wheelbase 56.8-58.0 in. Weight Fuel capeclty Suggested retail price , 227 Ibs. 2.2 gal. $2396 load up. It would pick back up quickly with a slip of the clutch, but this seems 10 be a tendency shared with the similar Bing equipped and pistonported Maico. Whether this is a quirk of the carburetor or piston-porting I couldn't say, since many of us have become so used to Mikuni carbs and reed valve. induction these last few years on nearly everything else. This isn't a problem at racing speeds, but riders do sometimes get sloppy and tired near the end of a molO. The chassis of the new MC·80 bike continues past KTM tradition. When it comes to attaching two pieces of steel chrome moly tubing together they continue to do it with the least amount of farsightedness and the maximum amount of gussets and brackets. The top backbone of the frame uses no less than four pieces of tubing running from the steering head back in a trapezoid arrangement. Everyone else gets the job done with just one or twO larger diameter tubes. What the MC-80 frame does impart, though, is brute strength and torsional rigidity - it will not flex. However, the 420 motor cannot be removed , from the frame without removal of the carburetor and swingarm. The ~est of the bike is really exciting. All the right goodies are there from an extruded aluminum swingarm, full floating conical rear brake, and heavy duty nylon blocked chainguide and roller to such trick goodies as folding brake and shift levers and a nonbreakable aluminum silencer. Fenders. tank and sidepanels are unbreakable plastic_ Levers are dog-leg Maguras and the throttle is the new 90 degree Magura assembly. Every component on the bike is premium quality right down 0 the American Sun rims and German Metzeler tires. Last fall when I tested the 250cc MC·80 I was not very impressed with its handling, due mainly to the way the suspension was set up. I was happy to find that the suspension on the 420 test bike was set up right and the entire bike handled beautifully. In stock form it seemed the equal of any factory works bike I have ridden. This really amazed me because the stock 10.8 inch travel Marzocchi air/oil forks used on the bike have never been the one brand of accessory forks everyone rushes out to replace on their own bikes to make them handle better. But the Marzocchis on this bike were dampened perfectly and the progressive spring rate was just right for small shudder bumps and big jumps. Since the forks were new and the springs hadn't settled in yet, no air pressure was used. Factory rider Bruno gains about a half inch of travel out of his Marzocchi forks by shonemng the topout spring. Earlier MC-80 bikes came equipped with Koni non-rebuildable reservoir shocks. but all the new bikes come with excellent Ohlins gas/eil shocks with external reservoirs. These are one of the best accessory shocks on the market today so KTM cOJ1ldn't have· selected a better one. The Ohlins have dual rate springs and a celasto progressive spring-rate-effect bottomout rubber. They're rebuildable and adjustable for both dam pint and spring preload (i.e, ride height). Rear wheel travel is 11.8 inches. The monster 420 proved to be a joy to ride, particularly as the new suspension components seated themselves in and began to soften up. The handling characteristics of the bike are very neutral, similar to those of a works Suzuki RN. allowing you to shift your weight to the back of the bike for better handling at speed, while for better low speed handling you shift yourself slightly forward and work the front end. There is no real need to crowd the gas tank since the front end tracks itself beautifully through the tightest turns, always on the chosen line without the need for more weight or muscle. Even on off ·cambers it sticks to your intended line. High speed tracking across rough ground also proved exceptional. As long as the power was on the bike would go straight. There is no flex in the frame or swingarm to kick you sideways. even over the worst bumps. The bike is not a wheelie machine and bringing up the front end requires a . conscious effort. The brakes were among the best I've ever encountered on any factory bike. Really strong, progressive and light to work. Even the smallish front conical brake was up to its task of slowing the big brute down from high speed without any effort whatsoever or the slight fear that it could put you over the handlebars if you got carried away and pulled on the Magma lever too hard. I f I keep making references to Japanese factory works bikes it is because the 420 KTM handles that well. Even its weight won't give it away. At 227 pounds it's lighter than the factory 420 Uni-Trak Kawasaki of Brad Lackey's (230 lbs.) and only six pounds heavier than Heikki Mikkola's ultra exotic OW-41 Yamaha (2.21 Ibs.). The 420 engine really is a monster. But it is a very tractable monster if you exercise very precise throttle control. The powerband begins pulling smoothly and strongly right from around 2,000 rpm to wherever it may go, perhaps 7.500 rpm. But the fear it instills in you is immense. Not totally from sheer horesepower, but from the engine's quick revving ability. Lean on the throltle hard and the engine will bum the rear tire ,,-s it scratches for traction. You don't want to be anywhere nearby, particularly in the rider's seat, if this mutha. ever decided to suddenly hook up with the ground. Rolling on the throttle slowly and precisely will allow the 420 to retain traction and accelerate forward. The problem with the 420's overly zealous, quick-revving tendency is twofold; the first being the 4.50 x 18 Metzeler rear tire is nowhere near capable of handling the power available. and the other is the low inertia of the small internal rotor Motoplat. The solution is to install either a larger 5.00 rear tire, a heavier external rotor Motoplat, or both. I'd begin with the larger rear tire, which is needed anyway, and it might, in itself, help to add a little more flywheel effect to the engine. The new Motoplat should only be considered as a last resort since the engine's powerband has more than enough torque to pull its way through or up anything_ You'll ·still have to learn that smooth and controlled use of the throttle is the way to win races. There is enough low speed power and tractability in the 420 engine that you never have to worry about using first gear. Second is. the lowest gear you-U use for tight turns and steep hills. Third gear can be used for staTts. I even tried a number of fourth gear starts which went off beautifully, though it required keeping the engine screaming and clutch slipping for a hundred feet or so. Third gear starts were quicker. 'In aU, the new 420 KTM is a fantastic motorcycle which is certainly equal to the works machinery being, used in World Championship motocross today. It's handling alld suspension cannot be faulted_ The basic 420 engine package is excellent as well, while the annoying problems of bogging when off tlJt, powerband and too quick revving when on it could easily be corrected with a different carburetor and a larger rear tire. •

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