This text is from the December 2000 difficulty of Motocross Motion Journal. Get your MXA subscription right now
QUESTION ONE: IS THE ‘01 ENGINE FASTER THAN THE ‘00?
Sure! It might be inconceivable for it to not be. Final yr’s engine had a lazy powerband that begged for an odometer and route chart. Excluding a bit burp of energy when rolling the throttle on, there wasn’t a lot to rave about on the 2000 KTM 250SX. It had a brief, flat, monotone-style of energy. The 2001 KTM 250SX is lightyears higher than the 2000.
QUESTION TWO: WHAT DID KTM CHANGE ON THE ‘01 ENGINE?
In fact, that they had modified virtually each a part of the engine for 2000, in order that they actually didn’t need to make very many modifications. But, that’s complicated. If the 2000 engine was a canine, why wouldn’t KTM change each facet of it. The reason being easy. Final yr’s engine suffered from a critical lack of improvement. KTM rushed the all-new engine into manufacturing with out dialing within the porting, jetting, head quantity or ignition curve. It wasn’t prepared.
Now, a yr later, they’ve had the posh of time to complete the R&D they skipped (or did poorly) final yr.
So what did they modify for 2001? Three little issues: (1) They reshaped the exhaust and increase exhaust ports. (2) The top quantity was decreased for crisper throttle response. (three) The piston has been lightened.
QUESTION THREE: WHAT DO THE CHANGES MEAN?
The 2001 KTM 250SX has an ideal engine. It produces considerably higher energy than final yr. The ‘01 Austrian engine has a broader energy unfold, is simpler to journey and carries momentum from gear to gear with aplomb. Each check rider liked the best way the engine ran. It required much less clutch work than any 250 two-stroke in current reminiscence.
QUESTION FOUR: IS IT AS FAST AS A JAPANESE 250?
You guess! Not solely is it as quick as a Japanese 250, it has a greater engine than most.
QUESTION FIVE: WHAT ABOUT THE JETTING?
Right here is the jetting we ran in our KTM 250SX.
Pilot jet: 48
Needle: NOZF NOZE
Air screw: 1 half?
Clip: groove quantity 4th
QUESTION SIX: WHAT ABOUT THE HYDRAULIC CLUTCH?
Hydraulic clutches are the wave of the longer term. As of now they solely come on European motocross bikes, however, excluding Honda, each Japanese bike wants remedial clutch assist (particularly Suzuki).
Don’t get too misty about hydraulic clutches although. They don’t do what most individuals assume they do. In case you suppose that hydraulic clutches are simpler to tug than common clutches, you’re mistaken. They aren’t. In case you presume that they really feel higher than a guide clutch, you’re fallacious. In fact, a hydraulic clutch is a bit firmer than the smoothest of the usual clutches and it has a distinctly totally different really feel.
What a hydraulic clutch does supply is a constant really feel over an extended moto. It resists the temptation to go slack, get mushy or tighten up. Though not completely resistant to lever strain variations, hydraulic clutches are extra constant than most guide clutches (with the potential exception of a CR clutch). Candy, very candy.
QUESTION SEVEN: WHAT ABOUT THE SINGLE-SIDED, NO-LINK REAR END?
Single-sided, no-link rear suspension techniques are additionally the wave of the longer term (though you possibly can return to the 1983 ATK to see the primary one). Why? Bikes don’t need to have difficult linkages, pivots, bearings and pull rods to realize the required leverage ratio change. By positioning the shock inside the recognized framework of a scalene triangle (one through which the edges have totally different lengths and angles) a suspension designer can duplicate the rising fee of any linkage system. Single-sided shock techniques are much less complicated, have fewer shifting elements, weigh roughly seven kilos much less (essential on a four-stroke) and are accessible. Maybe the most important benefit, and one which has nothing to do with the rear suspension, is that one-sided shocks make room for a straighter carburetor tract (which suggests extra horsepower).
QUESTION EIGHT: HOW GOOD IS THE 250SX REAR SUSPENSION?
KTM has made regular strides in dialing of their one-sided rear suspension system. Though they’ve made no modifications to the shock place during the last three years, they’ve utterly renovated the WP-built, however Ohlins-licensed, shock.
The unique concept of the PDS shock was to have two shock pistons that interacted at totally different factors within the rear wheel’s journey. One piston can be position-sensitive and the opposite speed-sensitive. Nice concept in concept, however completely atrocious in motion. To KTM’s credit score, they’ve been decreasing the impact of the second piston with every successive yr, to the purpose that it’s now used to regulate bottoming solely. Moreover, the WP rebound circuit has been revised so that a needle replaces the earlier valve (that is supposed to scale back thermal masses on the piston).
The rear of the KTM has a harsh feeling when new, however because it breaks in it begins to really feel higher. We had respectable luck with the inventory shock spring this yr.
What was our greatest shock setting?
Spring price: eight.three/ 11 kg/mm?
Race sag: 95mm
Compression: four clicks out
Rebound: 20 clicks out
Notes: Widespread sense and years of expertise inform a rider that turning the compression clicker in (clockwise) will stiffen the compression damping. Not so on a KTM. You flip the clicker out for extra compression and in for much less.
QUESTION NINE: WHAT DO WE THINK OF THE 2001 WP FORKS?
We expect they’re horrible. We have been somewhat miffed that KTM threw within the towel on its right-side-up forks in 2000, however stored an open thoughts. We should always have closed it. The upside-down WP forks need assistance.
The forks aren’t supple. They’re too gentle. Even worse, they backside after which bounce. The damping and spring price are poorly matched. The quickest repair for these forks is to drop the inventory zero.40 forks springs for stiffer zero.42kg/mm springs. Moreover, we lowered the oil peak from 130mm to 140 (which is the place it was final yr).
What was our greatest setting? For hardcore racing we advocate this set-up:
Spring price: zero.42kg/mm (zero.40 kg/mm inventory)
Oil peak: 140mm (130mm inventory)
Compression: 14 clicks out
Rebound: 14 clicks out
Fork leg peak: 10mm above triple clamp
Notes: In contrast to final yr’s typical forks, which had method bizarre adjuster placement, the brand new WP upside-down forks mimic Kayabas (compression on the underside and rebound on the highest).
QUESTION TEN: HOW DOES IT HANDLE?
The phrase “Italian handling” just isn’t a praise. Because the KTM is inbuilt Austria, it might’t be accused of getting Italian dealing with, nevertheless, at greatest it has “Common Market handling.” And, what precisely is Italian dealing with? It describes a motorcycle that goes nicely in a straight line, likes to slip round vast open corners and is efficient in sweepers. Nevertheless, an Italian bike (nee’ Austrian bike) is more durable to show than a locomotive.
KTM dealing with is an space that may’t be danced round. The Austrian bike doesn’t deal with like a Japanese motocross bike. That is most noticeable on tight, twisty tracks, however is equally evident in any sharp nook. It doesn’t flip as shortly as an RM, YZ, CR or KX. It’s higher to slip the corners, search the surface line and attempt to keep momentum.
Unusually, the lighter KTM 125SX and heavier KTM 520SX deal with a lot better than the 250SX. The 250SX has an enormous push within the entrance finish that must be fastened.
QUESTION 11: WHAT ABOUT THE NEW GAS TANK?
The perfect factor that KTM did to the 2001 KTM was redesign the fuel tank. The brand new unit is slimmer, sleeker and narrower than any tank made. It makes shifting round on the KTM simpler.
On the draw back, we might have appreciated a bigger fuel cap and orange plastic. The mixture of a teeny little inlet and darkish plastic eliminates any hope of understanding if the fuel tank is full or not. This can be a fill-it till you spill-it fuel tank.
QUESTION 12: WHAT DID WE HATE?
The hate record:
(1) Entrance fender: KTM’s entrance fender seems terrible.
(2) Fuel cap: The fuel cap is just too small.
(three) Rear brake: KTM claimed that they modified the rear brake to make it extra progressive. We now have little question that they modified it, however it isn’t extra progressive. It squeals and squeaks like a pig.
(four) Compression adjuster: Some check riders might flip the WP compression adjuster with their boot. The bike acquired stiffer because the moto acquired longer.
QUESTION 13: WHAT DID WE LIKE?
The like listing:
(1) Airbox: It’s cool to not should take away the seat to get to the filter. Watch the dzus-style fasteners–they disappear quicker than David Copperfield.
(2) Handlebars: KTM is the one one of many Huge 5 to return inventory with aluminum handlebars…not to mention over-size aluminum bars. Very cool.
(three) Body guards: KTM consists of plastic body guards on each bike.
(four) Preload ring: As an alternative of utilizing two rings, which lock towards one another, KTM has a really thick single ring which clamps to the shock physique by way of an Allen bolt. This can be a good concept and makes adjusting spring preload simpler.
(5) Clutch: It’s hydraulic. Sufficient stated.
(6) Chain adjuster: KTM designed eccentric chain adjuster blocks that may be rotated when the chain stretches. Moreover, they’ve a really lengthy axle slot to accommodate large wheelbase modifications.
(7) Bar mounts: KTM’s triple clamp options four-way adjustable bar mounts. This enables the rider to fantastic tune the match. We ran the bars all the best way ahead
(eight) Particulars: The KTM bristles with artistic extras. The motor mount nuts are caged so that you simply don’t want a wrench to carry them. The axle nuts are capped in order that the threads aren’t uncovered. The brake rotors are cauliflower-shaped to equalize warmth. The chain blocks are eccentric in an effort to change the wheelbase.
(9) Swingarm: Earlier KTM swingarms broke. The 2001 KTM has a completely new, one-piece, extruded swingarm.
QUESTION 15: WHAT DO WE REALLY THINK?
Final yr the KTM 250SX had “Euro handling and enduro power.” This yr, it has an superior engine…now, if solely we might do one thing concerning the cornering.