Not ones to rest on their corporate laurels, KTM has been a continuous technological force, leading the industry with innovations like power valves, USD forks, water cooling and other technological leaps of the 80s, and more recently ('95 model year) the first dirt bike manufacturer to return to conventional slider forks.
In response to the one lingering fly-in-the-ointment of recent years (ignition dependability), KTM has bid sayonara to the perennial SEM ignition for '97, replaced with a state-of-the-art Japanese Kokusan spark unit. Add to that the new mega-fork from Marzocchi, and it's easy to leap to the conclusion that KTM has another winner on its hands. A foregone conclusion, perhaps, but one that was easily proven during our extended testing. Here's what we've learned.
Our '97 KTM 250 EXC has been safely snuggled in the TR garages since December, and we've been trying to get a story out on it for two months running. Pre-empted by recent Kawasaki and ATK projects, in the interim we’ve continued to ride and wrench on the deuce and a half, and in the process left no bolt unturned. As usual, the bike showed up at the TR offices in a sturdily constructed, reinforced cardboard carton and as is often the case our first impressions of the steed were formed during the assembly process. This entailed mounting the fork and front wheel, installing the shock and various levers and controls, and making needed adjustments. First impressions of the fork are profound.
"The brutish new 50mm Marzocchi sliders are beefy and noticeably weighty."
Prior to mounting, we did a casual check of the fork oil level and found it to be overfilled on both sides. A good dealer would pick this up, however negligence here could easily lead to the seal leakage problems reported by many users of the new Zokes. With sano fork boots installed (and proper fork oil level), we experienced nary a problem with seal leakage to date.
A new front brake hose makes mounting enduro hand guards more difficult, especially when the bars are cut some. This is because the new hose screws straight into the master cylinder (as opposed to earlier hoses with a 90º bend at the master cylinder), monopolizing space otherwise needed for hand guard mounts or tie down hooks. Our modestly cut handlebars (about 30") gave us a handlebar space headache. A switch to an older model front brake hose could solve things, but who wants to shell out bucks to replace a functional brake hose? We made do, and otherwise, everything went together fine. With that, we were ready to kick up some roost.
Inevitably, when a new bike hits the trail, there's one defining characteristic that we end up spending most our time fiddling with. Honda CRs, it's the fork. Thumpers get put on a diet. With ATKs, RMXs, and surprisingly, this years 250 EXC, it's uncorking the motor; each however in a very different manner. Right off the bat, we found the '97 KTM 250 EXC to have an uncharacteristically flat power delivery in stock trim. No doubt, the term "electric" is way overused, often being a thinly disguised way of saying "slow," although the term does admittedly come to mind.
"A lot of riders like a little more pop for roosting out of deeply bermed corners or lofting the front end over typical woods obstacles, and fortunately, it's really easy to find that with this KTM."
This bike's not slow, it's just that it doesn't have a lot of snap when you rap the throttle. Of course, what this means is that you're not spinning the back wheel wildly and spitting gravel in all directions, but instead maintaining good traction and propelling forward. Works great for some riders and some conditions. Still, a lot of riders (this author for one) like a little more pop for roosting out of deeply bermed corners or lofting the front end over typical woods obstacles, and fortunately, it's really easy to find that with this KTM. Before we launched into that quest, however, we cleaned up the carburetion some. For the record, the Keihin PWK 38 carburetor comes from the factory with a 48 pilot, 175 main, N85C needle with clip in #3 position (from the top).
Jetting was a little sloppy like this, especially down bottom, so we gave Mike Lafferty a call and he passed on his race bike jetting specs, a leaner 45 pilot and the needle raised to the #4 position (with the stock 175 main). We've had good luck with this jetting and it should be fine for just about everyone. It's been noticed though, that the bike does seem a bit sensitive to changes to temperature and fuel quality. As might be expected, the RFG pump fuel we get here in northeast corridor confounds jetting and sometimes leads to pinging at high speed while under load. A switch to race gas, 115 octane CAM2, made a tangible difference.
Another note, some bikes have been reputed to come with crud clogging the pilot, confounding low speed jetting. If you can't seem to get the low speed jetting right, drop the float bowl and give a look for obstructions. Throughout the duration of our TR testing, a single plug was fouled, and that was with the stock jetting. Since then, it's been clear sailing. With jetting straightened out, it was time to look for some bark, and a freer flowing silencer is one trick to opening up this pony.
A Dyno Port cheater silencer and a free flowing KTM MX silencer were tested and both provided tangible gains right where needed. More grunt off the bottom, more snap in the midrange. Both non-OEM silencer options increased the noise level slightly, however not as much as you might expect. Bear in mind that the stock silencer/spark arrestor is beaucoup quiet and is a tough act to follow. The noise differential is most noticeable at idle and just above. At normal riding speeds, the difference is negligible. Pipe changes were also contemplated, and in the past we've had good luck with Dyno Port torque pipes and FMF offerings. However, the nickel plated stock KTM unit makes good power and looks great. Factory KTM riders like Mike Lafferty and Scott Plessinger use the stock pipes and that's enough of an endorsement for us. Perhaps after we bash up the stocker we'll do some actual aftermarket testing and report on it accordingly.
Unfortunately, after all the re-jetting and aforementioned exhaust fiddling, we were starting to get worried. Where was the ample KTM enduro power, common on earlier models? Sure, the '97 motor is smooth, no doubt great for really slick and snotty conditions, but it just didn't have the kick needed for high traction work. A stab of the clutch when exiting a tacky bermed corner left test riders sorely disappointed. Clip suggested the ignition, so we got on the horn with KTM factory mechanic Tom Moen. It turns out the new ignition makes this the most radically different KTM motor introduced since the switch to left side drive (in 1989). The new KTM-spec Kokusan unit is used on all of the ‘97s (excepting 125s), both off-road and motocross models.
Off-road and SX ignitions differ in three ways: a different advance curve (milder on the EXC); lack of a lighting coil on the SX; and the addition of a bolted-on flywheel weight (for EXCs) on the otherwise common flywheel. Also noteworthy, there are only two different ignitions (SX vs. EXC) as all models (read: 250cc, 300cc and 360cc motors) share their respective ignitions. This is key, as Moen revealed that the designed flywheel effect for the EXC models (and perhaps the SX models as well) were for the worst case (read: 360cc motor application). As such, it's generally accepted that the weighted flywheel is kind of heavy for the 250cc power plant.
Sniffing a trail, we dug deeper. A '96 250 EXC flywheel was compared to the '97 flywheel assembly using the trusty TR bench scale. The results were startling. The '96 EXC flywheel weighed in at 655 grams, about 23 ounces. The '97 flywheel assembly (flywheel and bolted on weight) a whopping 912 grams (32.1 ounces)! Once separated (no easy feat) the bare ‘97 flywheel weighs 552 grams (19.4 oz.), while the flywheel weight itself tips the scales at 361 grams (12.7 oz.). What did all this tell us? The unweighted '97 EXC (and SX model) flywheel is less than 4 ounces lighter than the earlier SEM-equipped KTMs, while the stock EXC weighted flywheel assembly weighs almost 10 ounces more (editor's note: it's granted that weight is only one factor (a big one though) in determining flywheel effect, the other being how the weight is carried, which is affected by flywheel shape. The SEM flywheel is a greater diameter than the Kokusan flywheel, and likely develops additional flywheel effect as a result. However, this is fodder for engineering class, not a bike test and the truth is plainly evident with our test riding).
"Bottom line, the removal of the bolted-on flywheel weight really wakes up the ‘97 250, and is by far the single most important modification to turning this bike into a woods racer."
PAGE 2The flywheel weight is held on with four socket head (4mm) counter-sunk screws that are majorly lock-tighted and a bear to get out. Rest assured though, it's worth the effort. Mind you the weightless flywheel didn't turn the bike into a motocrosser, as the advance curve is still the milder of the KTM ignitions. Nor has the bike proven easier to stall. In our humble opinion, this is the hands-down ticket for the '97 250 motivator, and the clincher is, it doesn't cut into your beer money in the process.
Suspension and Handling
In the handling department, the good news is the '97 250 retains its nice manners and continues to be plush over woods obstacles, a good turner and very stable steed. Even in the rough stuff with the suspension working and things flailing, if you keep your butt off the saddle, the bike stays on-line and provides an easy-handling platform. The new 50mm Marzocchi Magnum fork again employs independent left and right side damping duties, the left fork leg taking care of compression damping while the right side does rebound. The 50mm Magnum fork has 15mm less leg underhang than earlier Zokes, while maintaining 11.8 inches front suspension travel.
This is partially accomplished with a revised "gull wing" triple clamp design. An Ohlins rear shock is back for '97, updated with a larger reservoir; alleged to improve damping by giving the shock more oil to work with, and thus reducing fade. Rear suspension travel is 13.4 inches.
During our initial excursion shooting pictures, we were somewhat shocked when the 250 exhibited excessively soft suspension action at both ends, resulting in severe bottoming while jumping the bike during the photo shoot. Increases in compression damping at both ends was a temporary solution. Factory fork clicker settings finds 14 detents, adjustments accomplished using those sano blue knobs on the top of the fork leg. Factory set fork compression (left leg) damping was in the # 6 position (from full soft--CCW, minimum damping), and fork rebound (right leg) set at 10 clicks from full CCW.
Our knee jerk reaction bumped the fork compression leg to maximum compression, although we softened things somewhat since then, eventually migrating back to the #6 (surprise!) stock position. Rebound damping was softened somewhat as well, our final position (as of this writing) being five clicks out from full soft (full open/counter clockwise).
"Remember when spinning the Zoke damping adjustments, it's better to turn out the adjuster to full open (CCW) to begin any clicker adjustments."
Since the adjuster is a needle and seat assembly, any manhandling the clicker into the full closed (CW) position unnecessarily runs the risk of deforming the seat and ultimately confounding all damping adjustments. We found that with the fork compression and rebound damping cranked up, the bike worked pretty well when dealing with stadium-type obstacles--good in the whoops, big landings, but not-so-good over roots and logs, and a little stiff during the initial hit. With the current softer settings, the fork is plush, but still worthy of top level woods racing.
Air buildup, especially in the compression leg is still a problem, and when setting the fork up, be sure to rotate the fork leg so that the bleeder screw can be easily accessed. We witnessed riders bleeding the 50 mil Zokes on the trail, resulting in the fork settling (static sag) an additional 30-40mm! Likewise with the Ohlins shock we went gonzo after bottoming the back end during that first ride, and then eventually, succumbed to reason. The Ohlins unit provides 27 clicks of compression adjustment, set at 17 clicks from full hard (CW) from factory. Like with the fork, we increased compression damping (to the #14 position) and eventually worked our way back to the stock #17 detent.
The rebound adjuster likewise provides 24 choices for damping, factory standard set in the #18 position. Quite frankly, the suspension works great as set up as above, a fact proven under the duress of the recent ECEA opener Sandy Lane Enduro, and we’d be happy to keep racking up the mileage as is. However, we're about due for a fork oil change and it so happens that factory mechanic Tom Moen had some interesting recommendations in this area as well. Moen recommends less rebound to reduce packing on braking bumps, which seems to be better accomplished using thinner oil in the rebound leg, versus just reducing rebound damping. Stock ten weight fork oil is replaced with 7.5 weight in the rebound leg, and five weight in the compression leg. Maybe in an issue or two we'll have tried this and have the good word on it.
Aside from setting the fork oil level properly during assembly, our suspension and handling testing has been limited to the above clicker spinning and the installation of a WER steering damper. While not universally convinced of the merits of steering dampers for all situations, this WER unit is especially trick because it allows for a clean relocation of the ignition brain box, allowing the fork stops to be readjusted for tighter turning.
With respect to handling improvements, we were impressed by the additional stability offered by the steering damper-equipped KTM through deep, soft whoop-de-dos. Turning prowess was sharpened a bit by raising the fork in the triple clamp. Our initial setup started with fork cap/slider junction even with the top of the triple clamp. In this configuration, the front end pushed (on occasion), a situation perhaps confounded by the intermediate terrain Pirelli MT18 tires. This lead to some fantastic get-offs. To increase front end bias, the fork was raised in the triple clamp to the first notch in the slider resulting in better steering manners with no discernible effect on stability at speed.
The '97 250 EXC comes fully equipped with all of the enduro trim we've come to expect. Headlight, tail light, license plate mounting, resettable odo, wide ratio 5-speed tranny, and a large fuel cell (13 liters) with a reserve position petcock. The only drawback is that the new EXC ignition lighting coil generates a mere 35 watts accessory power, versus the 130 watt lighting capacity provided by the old SEM ignition. Also, the Kokusan ignition mounts the brain box on the side of the steering head, in-between the triple clamps, reducing adjustable steering and confounding the installation of some steering dampers. Some riders remount the black box beneath the tank, while the WER steering damper solves both these problems with a trick mounting bracket that relocates the ignition box.
The '97 saddle comes with softer seat foam and a trick textured seat cover that provides excellent adhesion for the derriere. Plastic is adorned with a tasteful graphics update, black, gray and white stickers on a somewhat tamed orange-colored plastic (we thinks it's a lighter shade of orange). Finishing touches include Domino controls equipped with rubber boots to keep out dirt and water. Clutch action is excellent, with a nice smooth delivery that makes it easy to feed in the power. Sturdy aluminum shift and brake pedals and fine aluminum handlebars round out a top quality rider interface.
"The '97 KTM 250 EXC is a worthy mount for beginner or expert alike."
Unchanged from previous years, DID O-ring chain is standard on off-road models, driving steel front and aluminum rear sprockets. Stock 14/52 gearing keeps the motor in the meat of the powerband in nearly any situation, while dependable Brembo braking components provide good stopping power and feel at both ends. The '97 KTMs come shod with Pirelli MT18 tires which aren't bad all-around tires, but slanted more toward hard terrain, and they definitely give something away in loose sand and slick mud. The MT18 front meat pushes and eventually breaks away, while the rear tire spins without biting. We'll swap between our perennial favorite Dunlops in the sand and Trelleborgs in the rocks.
Regarding maintainability, a new radiator shroud mounting scheme eliminates problems associated with the old captured nuts. The new retaining nuts are crimped into the radiator mounting tabs and provide a very positive mount for shrouds. In an attempt to improve spark plug access, KTM installed a unique shorter spark plug. While this makes plug changes somewhat less of a hassle (not much), the plugs themselves are hard to find in non-KTM shops. After fouling the stocker, we installed a common NGK B8EV and have been running that plug ever since.
Our conclusion? The '97 KTM 250 EXC is a worthy mount for beginner or expert alike. Novice riders can leave on the flywheel weight for nice, controllable, but spirited power delivery. Hard chargers will ditch the flywheel weight in some conditions and perhaps bolt it back on for others. In all, it's a great bike and I hope that we get to hang onto it all season long. What are we going to do? Race the hell out of it and take names!
With a little luck we might even see an up-and-coming eastern enduro racer by the name of Mike Lafferty pilot a near-stock 250 EXC to the ‘97 AMA National Enduro Championship, but that's a story line yet to be played out. Either way, 1997 is shaping up to be a banner year for the folks up in Lorain, Ohio, and we're looking forward to being along for the ride.