2003 KTM 125 SX from United States of America


Hang on or fall off


Nothing majorly wrong has happened with this bike.

The stock clutch levers are weak and should be upgraded, but other than that, the bike performs great.

General Comments:

This bike is insanely fast from the start; the acceleration is almost like riding a 500 2 stroke and it's insanely smooth to ride. I've loved the bike ever since I first rode it.

Would you buy another motorcycle from this manufacturer? Yes

Review Date: 31st October, 2018

2003 KTM 125 SX from United States of America


Worth every penny



I replace the top end every 50 hours or so. Did I mention I race regularly in the MRANN Desert Series in the B class (Expert) with this bike? I have never had a race that I did not finish due to malfunction. I race in 100 plus heat and over 100 mile races, and never had it overheat even on the most grueling enduros.

If you maintain the bike properly, replace chains and sprockets, the occasional seal or gasket here and there, you will never have a problem with this bike. There is a reason KTM is the number one selling bike in the world and now in the U.S. They are RACE READY as KTM advertises.

General Comments:

The 2003 KTM 125 SX is a dream of a dirt bike. I have been riding since I was 6 years old - just turning 30 - and I have owned over 6 bikes, both 2 and 4 strokes from practically every make and model. I have bored this engine out to a 144cc and changed the gear ratio to fit it. I live in Northern Nevada in the high desert, and once you jet the bike correctly for your altitude and run the proper fuel ratio (40:1 for me... some run theirs at 50:1, but this is all relative to one's elevation jetting etc), you should never have any trouble - EVER - if you do, you unfortunately got the occasional lemon off a production line or it's your own fault. These bikes are very easy to maintain and really don't require much maintenance to perform well. Proper maintenance, as common sense would tell you, just makes it that much more reliable.

It is extremely fast for a 144cc, lots of low end, enough top-end at 70 mph and revs to the moon! It is light and nimble in tight sections, and smooth and forgiving in wide open and "rock-gardens" due to its ability to lug down low and rev back up at the drop of the clutch. There is a reason as well that most Pros race 2 strokes in off-road. Many of which they ride 150cc-300cc depending on the environment... They work. It will be hard for me to ever race a Japanese bike again off-road.

Would you buy another motorcycle from this manufacturer? Yes

Review Date: 25th September, 2014

2003 KTM 125 SX from United States of America


Above average


The one thing so far that I didn't like was the oil drain plug on the right side. Too easy to strip out by over tightening. My fault.

Guess I could say I don't like the bolts that stop the triple tree from hitting the frame. I have bent many of these. Where the bolt screws in is getting bad... but still works!! Crushed the e-box by the neck also.. but still works!!

Worries me about the chain being so close to the hydro clutch too. But once again, no problems.

General Comments:

Very happy with the bike. Very nimble, and light to handle. Quick enough, and makes a nice trail bike with the right sprocket.

One of the best web sites for support groups out there. Any questions are answered. This is a big help and makes the bike worth more... to me.

Would you buy another motorcycle from this manufacturer? Yes

Review Date: 30th September, 2006

11th Mar 2007, 18:57

What would be better for woods riding and racing, the KTM 250sxf or the KTM 125sx?

31st Mar 2007, 23:59

I own a 2003 125 SX and it is an absolute weapon off-road.. it has immense acceleration (quicker than my friends 250 SX-F) and is so much lighter and flickable through trails it makes his SX-F boring (literally).

As long as you jet it right, it will not foul plugs, and has awesome low end power and will chug along like a tractor all day. The performance for a 125 is breath taking, and the sound it makes echoing thru the woods is awesome!

Look at most of the top professional off-road riders, they prefer the two-stroke... the smile it will put on your face is worth it alone.. they are the cheaper and better choice.. 125 SX all the way!!! You won't be disappointed, GUARANTEED

9th Apr 2008, 21:51

What is the oil to fuel ratio on a 2003 125sx?


27th Jan 2009, 09:06

50:1 - 60:1, put 1 pint of best brand two strole oil in a six gallon jug and fill with premium or better fuel, works fine in both a 2003 125 SX and a 2004 250 SX...

16th Feb 2009, 22:13

I was wondering how easy these bikes are to maintain, and if so, does it cost much to maintain? Thanks.

4th Oct 2009, 14:50

I just recently purchased a 2003 KTM 125 SX, and I am 23 years old. I also own a CR 250, and the KTM is almost as good on the trail and the track as the CR 250. It's fast and has great power.

10th Mar 2010, 18:58

I just got my 2003 SX125, and it has great power, but I've fouled two plugs running 40:1 with blue marble. The bike has great power. I've moved up from a CRF150R. Can't wait to race.

2nd Apr 2013, 20:15

A KTM 125SX is best for that.

20th Sep 2018, 12:26

Yeah always run 50:1 with premium gas. I usually just pour a 12 oz can of oil into a 5 gallon can of premium and my bike runs like a dream.

2002 KTM 125 SX from United States of America


Fast when it runs, when it runs


4 pistons all during racing, finished very few races.

1 jug, miked it to find it not round.

Still uses pistons like most bikes use plugs.

General Comments:

Never in my riding life of over 40 years have I been around any motorcycle that demands more service than this KTM.

Would you buy another motorcycle from this manufacturer? No

Review Date: 26th December, 2005

9th Mar 2006, 17:26

I have to think there is a problem at the crank. Yeah, we all get a bad vehicle sometimes.

7th Sep 2006, 17:50

I hav owned a KTM 125 SX since 2002. I ve only had to rebuild it 4 times since new. I only race every second month, and the bike has been nothing but enjoyable.