ON THE RECORD: COMPLETE TEST OF THE 2004 KTM 125SX

2004 KTM 125SX This article was pulled from MXA’s 2004 bike test archives.

If you’ve ever stood in the first turn at an AMA 125 National, you’ve seen a horde of orange bikes fan out across the track. It’s evident for all to see that the KTM 125SX makes a lot of power. We know what you’re thinking: “those are factory bikes and you can’t compare them to what you can buy off the showroom floor.” You couldn’t be more wrong. Even factory bikes have to start somewhere and it’s easier to make a fast bike faster than to pull a rabbit out of a slow hat.

For the record, the KTM 125SX has the best two-stroke engine in the class. It puts most Japanese bikes to shame on the dyno, in first turn drag races, and up hills.

So, what could the Austrians do to improve the 125SX? They could listen to their critics. While the 2003 KTM 125SX engine ran great, it only lived up to its full potential after you put an aftermarket pipe and silencer on it. The WP suspension, while light years better than the previous Dutch crud, was still struggling to come up to what they had achieved years before with Marzocchi.

It seemed so simple to us. Put a pipe on the engine, work on the suspension and fix a few niggling gripes. That’s what KTM should have done for 2004. But, what did they really do?.

Q: WHAT DID KTM DO TO THE 2004 125SX ENGINE?

A: They did as little as humanly possible. The only serious complaint about the powerband last year was that most MXA test riders wanted more overrev. We got it in 2003 with a Pro Circuit pipe and silencer. That bolt-on was good for an extra horse or two.

The Austrians may be slow to change, but they aren’t oblivious when it comes to horsepower. So, rather than change the porting, revise the power valves or double shim the widget, they bolted an aftermarket pipe on the 2004 (only instead of using a Pro Circuit pipe they copied a European Doma pipe).

The 2004 KTM 125SX engine pulls incredibly hard in the middle and continues to make excellent power into the top-end.

Q: THEY MUST HAVE DONE MORE THAN THAT TO THE 2004 ENGINE?

A: You bet they did! Once they got bitten by the real world bug, they discovered that most KTM 125SX owners were putting Moto Tassinari VForce reed cages on their bikes (we had one on our 2003). We did it last year to get a better low-to-mid transition and quicker throttle response.

The KTM engineers decided to buy the American-made reed cage and make it the OEM part. The result? The bolt-on Doma pipe and Moto Tassinari reed cage got KTM two more horsepower over their 2003 model.

Think about that for a second. The 2003 KTM 125SX made the most horsepower of any 125 two-stroke and this year it makes two more ponies. That’s massive.

Q: HOW DOES THE 2004 KTM 125SX REALLY RUN?

A: No surprises. It ran just like MXA‘s full-race 2003 KTM 125SX. It pulls incredibly hard in the middle and continues to make excellent power into the top-end. Don’t get us wrong, we still wish it had more over-rev (and we intend to remove the Doma pipe and put our 2003 Pro Circuit pipe on the 2004 to see if we can get it back). But, as it sits on the showroom it’s the fastest two-stroke around.

Q: WILL IT KEEP UP WITH A 250 FOUR-STROKE?

A: If any 125cc two-stroke can, it will be the KTM.

Q: IS THE STOCK GEARING SPOT-ON?

A: No. It’s close, but it doesn’t get a cigar. The MXA wrecking crew waffled between the stock gearing and one more tooth on the rear. The choice depended on the track layout, dirt conditions and altitude. For most Novices and Intermediates, one tooth is a plus. Pros will be able to carry the stock gearing.

It took KTM six long years to take a step in the right direction to fix the horrible PDS rear shock. 

Q: IS THE 2004 KTM 125SX BETTER THAN LAST YEAR?

A: Yes. Obviously. The engine has been brought up to USA racing standards (thanks to the pipe and reed block), but the biggest improvements are in the suspension components.

KTM owns the Dutch WP suspension company. And, while WP may know something about building suspension for Holland, they don’t know doodly about American requirements. Ever since WP got the KTM contract, and they didn’t get the purchase order on merit (more like nepotism), KTM’s suspension has been horrendous.

Much like the Showa/Honda improvement of 2002, WP and KTM have suddenly gotten a clue. We can’t say that they have made a complete turnaround, but for a change the WP forks are actually under control for the full length of their stroke. They are a little soft for Intermediate and faster riders, but for most 125 pilots the forks are the best we seen from the Austro-Dutch Connection.

Q: WHAT ABOUT THE WP PDS SHOCK ABSORBER?

A: Hallelujah! It finally moves. If you’ve ever ridden a KTM you know that the rear shock chatters like a jackhammer through small bumps, while offering no visible sign of movement over big jumps (until it bottoms). It’s jarring. It’s confusing. Too hard over little bumps. Too soft over big jumps. And, no sensation of suspension in between.

Every MXA test rider hates KTM rear suspension—and they aren’t bashful about complaining. We didn’t like it in 1998, ’99, ’00, ’01, ’02 or ’03. Not that we didn’t try to fix it. We did. We just never felt that KTM was trying very hard. Finally, six long years later, they have taken a step in the right direction. What took them so long? For ’04 KTM did what most hardcore KTM racers did last year. They dropped the progressive-rate shock spring in favor of a 7.2 kg/mm straight-rate shock spring. We never understood KTM’s infatuation with progressive-rate shock springs. They rarely work, and they definitely contributed to many of KTM’s previous faults. To help the straight-rate spring, KTM re-evaluated the position- and speed-sensitive possibilities of the PDS shock valving. Over the last five years they had neutered the position-sensitive half of the valving, but for ’04 they reinstated it. How was it? Vastly improved. What’s the best thing about the ’04 KTM 125SX rear suspension? It actually moves. An important thing to know about the rear suspension is that you should always set the sag to 110mm. Any less and the bike has a stinkbug feel. Also, the rebound is touchy. If the bike is kicking you should slow down the rebound one click at a time.

Back in the day the Austrians didn’t take the American market seriously. It wasn’t until 2004 that KTM started listening to the American critics. 

Q: WHAT DID WE HATE?

A: The hate list:
(1) Front fender: Without the optional front fender brace KTM’s front fender hits the front tire every time you land from a jump. It is very annoying.
(2) Bar position: For some reason KTM ships the 125SX with the bar mounts in the forward bolt hole. That’s way too far forward. Put the bar mounts in the back holes and rotate the bar mounts forward; you’ll be happy. Thankfully, KTM spec’ed taller handlebars for ?04. Last year’s bars were way too low.
(3) Number plates: This is more hoax than joke. The numbers that most American riders want to use, don’t fit. We hate to say it, but you should buy minicycle numbers for your KTM.

Q: WHAT DID WE LIKE?

A: The like list:
(1) Engine: For the last few years KTM has had the best engine. It is powerful, broad and about the only two-stroke that can keep the YZ250F in sight. It’s gotten better in 2004, if you can believe that.
(2) Accouterments: With four-position triple clamps, Renthal Fat Bars, Renthal dual-compound grips and plated exhaust pipe, the KTM 125SX spells quality.
(3) Suspension: We never thought we’d see the day that the shock actually moved. In essence KTM did what all the local racers were already doing to their shocks. The forks could use stiffer springs, but they have a nice feel to them.
(4) Hydraulic clutch: We like it.
(5) Handlebars: Last year KTM lowered the bars by 10mm and ruined the ergonomics of the bike. This year they put them back where Americans wanted them.

Q: WHAT DO WE REALLY THINK?

A: The Austrians have never taken the American market seriously. Oh, don’t get us wrong, they liked the dollar versus schilling exchange rate, but they didn’t want any lip from Yanks about how to fix their bikes. Suddenly, that attitude is changing. KTM is actually listening to their critics. For the 2004 model year they have made changes that American riders asked for. The result? The fastest 125 two-stroke engine on the track. Better yet, it has the fit, feel and finish that American racers can appreciate. Nice work, mein Herr.