The Motorbike Archives

That's all changed now. After struggling with that original chassis for a few years more, Bombardier finally juggled some of the critical frame dimensions, bolted up the best suspension components the bike had ever seen and built the most tractable 250 motocross engine in Can-Am history by decreasing the bore and increasing the stroke. The 1978 MX-4 250 was the result, a motocrosser that at last seemed to be free of the traditional Can-Am eccentricities. That reborn motorcycle has been even further improved for the 1979 season. It's now called the MX-5. And with it, Can-Am's status in the ever-changing culture of motocross has ranged the entire spectrum, from also-ran to catch-me-if-you-can.

As in the past, the engine is what sets the Can-Am apart from the rest. The long-stroker generates just as much horsepower as the short-stroker ever did, but the present engine has a smoother delivery and a wider powerband. These changes have taken what already was the most energy-charged 250 powerplant in existence and tamed it into one of the best motocross engines made today.

The MX-5's widened powerband is easy to regulate, yet the characteristic Can-Am top-end power can still launch you down a fast straightaway like a low-flying ICBM. The only thing that should pass a 250 MX-5 on the straights is another 25() MX-5. If the magnesium-crankcased Rotax-built motor is at a loss for anything, it certainly isn't horsepower.

Nearly the only way to trouble the 32mm Bing-carbureted engine is to drag the revs clear down almost to idle and then dump the throttle wide open in a high gear. Since that's not something you're regularly called upon to do in motocross, the slight loading up that results shouldn't pose any problems.

Be as indelicate as you like with the shift lever, though, because the engaging-dog angles on all the MX-5's transmission gears have been modified to alleviate some sloppy shifting habits that bothered the short-stroke series. The clutch, too, is stronger due to the addition of another pair of plates to increase the friction area. And the fiber-coated drive plates are now made of steel rather than alloy to reduce the chance of heat-induced warpage.

Rising above the applause for the engine, though, is real news, the announcement that the uncatchable Can-Am engine has finally been encased in a chassis that does more than just connect the wheels. No Can-Am has ever handled as nimbly as this one, and none before has steered so flawlessly. For that matter, only the very best-steering motocrossers in the business can match the MX-5 for pinpoint accuracy. It magically seems to find traction in all types of turns and on all varieties of terrain almost without regard for slick sections or ruts.

As drastic as the improvements in handling are, the mechanical differences between the MX-5 and its predecessors are not all that radical. The adjustable-angle steering head that had become a Can-Am trademark has been done away with in favor of a conventional tapered-roller arrangement with a fixed head angle. Those who still want the adjustable head can swap back to that old style, but the entire steering stem and bearing assembly, including the special adjustment cones, must be bought and installed. But why mess with it? The 29.5 degrees of steering angle and 4.9 inches of front wheel trail seem to be spot-on.

Last year, the MX-4's swingarm pivot was repositioned lower in the frame to cure the radical downward angle of the arm, which was felt to be a culprit adding to the Can-Am's handling problems. This year, the MX-5 swingarm is at the same angle but an inch longer. The longer arm effectively places more weight on the front wheel, which assuredly contributes to the new model's improved steering. And since the extra inch was tacked on behind the lower shock mounts, the rear wheel travel was increased from just over nine inches to exactly 10 inches.

Can-Ams are reputed to have marginal suspension components for all-out motocross abuse, but again, the MX-5 breaks the tradition. Girling gas-emulsion shocks keep the 5.00 x 18 rear tire on the track, and a Marzocchi air/spring front fork makes good use of the precise steering. Between these two well-designed suspension systems, the Can-Am handles forgivingly on nasty ground and is reasonably comfortable everywhere.

The Marzocchi fork is fundamentally the same as last year's unit, but the MX-5 version has air caps, an increase in travel from 10 to 10.8 inches and a reduction in damping rates. Can-Am recommends 15 psi static air pressure in each leg, but we got the best results on our tracks using only about eight psi. The reduced pressure gave the fork just enough bottoming resistance for my 160-pound frame without making the ride too harsh on most bumps. Our 195-pound rider was happiest with about 12 psi in each fork leg. Lighter fork oil will improve upon our major complaint with the Marzocchis, which is their slightly harsh behavior on stutter bumps and other square-edged obstacles.

The British-built Girling shocks behave superbly on stutter bumps and ripply ground, but I got them to bottom regularly on big jump landings and occasionally on some of the slammable berms. Springs with a slightly higher rate would undoubtedly clear up the bottoming.

As delivered, the responsive Girlings keep the rear wheel in contact with the ground where all that power can do some good, but after 15 minutes or so of hard riding, the small-bodied shocks build up enough heat to fade noticeably. At that point the damping goes away badly enough to make the back end a bit bouncy. The shocks are really only adequate for short motos, and even then, only with a rider of no more than 160 pounds on board.

The Can-Am's brakes are unchanged this year, and for the most part they are completely capable of stopping the 218-pound racer adequately. Though they're not particularly powerful, both brakes are consistent and predictable. They become virtually useless, however, once they get wet, and they'll stay that way until thoroughly dried out.

There's another brake-related problem, this one with the Magura front brake lever and its plastic cable-adjuster locking wheel. Every few laps, the wheel would work loose and allow the cable play to continually increase—which is not a handy feature on a motorcycle that can go as fast as this one. Throw the plastic locking wheels away and replace them with the steel wheels that come on most other Magura levers.

With all the things Can-Am has gotten right on the MX-5, there are still a few unsolved problems, with the air cleaner at the top of the list. The elements—a K&N pleated gauze filter covered with a removable outer foam sock—get dirty quickly, since they are mounted outside the air-box. Their location also allows moisture to get past the elements too easily when riding in deep water.

Our test MX-5 blew its right fork seal the very first time we rode it, and we also had some problems with a sticking float needle. One tester whined about burning his leg on the upswept exhaust pipe, and another complained that the crude-looking footpegs were slippery when wet. Certainly not insurmountable problems, but ones to be remedied at the factory.

Many other areas do show careful design. The drive chain tensioning device is similar in function to the effective Husqvarna arrangement. The Sun rims are some of the strongest available and thus help reduce required spoke maintenance. The Super Trapp muffler is a forestry-approved spark arrestor which doesn't take the edge off the power output. And the MX-5 even has lighting coils built into the Bosch CDI stator, just in case you want to fit it with an optional lighting kit and turn it into an exceptionally fast enduro machine.

With lights or without, the Can-Am is the fastest 250cc dirt bike on the planet. Even most Open-class bikes can't keep up with it on a straightaway. Which means that, engine-wise, this Can-Am MX model is like every one before it. But that's where any similarity between the old Can-Ams and the new one ends. The bizarre handling is gone, as is the highly criticized suspension and no serious problems exist anywhere on the bike.

The MX-5 is the first truly competitive Can-Am 250 ever, a fact which is overshadowed by its status as one of the most totally competent motocrossers you can buy. Riders wise in the ways of previous Can-Ams will be skeptical. They'll find it hard to believe that any motocrosser that came from the Bombardier factory will do all the things we have claimed. But one ride will clearly show them that a new generation of Can-Ams does in fact exist. The handling should convince them. So should the steering. But if those two fail, there's always the unforgettable Rotax Rush. On a motorcycle that does everything else well, that'll get 'em for sure.■

RIDE REVIEW

If the 250 MX-5 doesn't have enough power for your tastes, you need a Pro Stock drag bike, a competent therapist or a cage. At 195 pounds, considerably above average for motocross riding, I constantly found myself getting hurled—wide-eyed with disbelief—past much larger motocross machines being ridden flat-out by much smaller riders who thought the idea of such a thing more preposterous than I did. Words alone cannot describe the ease and yet the ferocity with which the Can-Am accelerates. You've gotta try it to appreciate it. Can-Am motocrossers have always had mindbending power, but the new long-stroke motor and the rethought chassis at last see eye-to-eye about how to get around a racetrack. The horsepower hooks up to the ground as effectively as the very best 250 moto-tillers, and the MX-5 now steers right up there with the Maicos and the SWMs and the Hondas. The bike is no longer a conglomeration of seemingly unrelated pieces pulling in all directions. For the first time a Can-Am is a team, a collection of wonderfully orchestrated parts working to cut your old lap times to ribbons. And for the first time I can honestly say that in my opinion, here is a Can-Am with no bad habits whatsoever.—Paul Dean

There's one important thing about the Can-Am 250 MX. It has to do with speed. You see, it seems like every first-time rider of this Can-Am pulls into the pits after his first lap and a half. Generally he's wearing a 1000-yard stare. Suddenly he begins adjusting the brakes tighter. He does this because this bike is so utterly fast, that the most important thing in his mind has become his ability to slow the thing down.

Sure, I realize that the new Can-Am engine's powerband makes the bike far more controllable than ever before. The new frame geometry also insures that the Can-Am likes to go around corners. Nevertheless, this motorcycle isn't for novices or uncommitted riders. The message in this two-wheeler is the distilled essence of speed.

Accomplished riders will be able to exploit the Can-Am's power to outdrag any other motocross bike. That's a sizable advantage. But me, I'll spend most of my time in the Can-Am's saddle wondering if I've got enough brakes to slow me down for the corner coming up. In fact, I'm thinking of equipping this bike with a parachute and retro-rockets for emergencies.—Michael Jordan