20 Most Recent 2003 KTM SX 125 Questions & Answers

your pilot circut is clogged. Take out your pilot jet (this is the jet closest to the cylinder) Be sure to spray carburator cleaner thru this jet until the stream is heavy and solid. Next insert the tube from your can of carb cleaner into the hole the jet was in and spray until it comes out in two locations in the carburator. One in the throat of the carb and one directly under the front edge of the slide. Go to the back of the carburator and you'll see a couple of holes at the bottom edge of the carb that mounts to the air box. these are vent holes. Spray cleaner into them and find the hole that vents the pilot circuit and insure it is not clogged. Once all of these are cleaned your bike should run as if new. Good Luck.

Replace the spark plug first. Cheapest/easiest thing to try and most popular failure on a two-stroke. If you still don't have spark from the coil wire, then you have to troubleshoot the coil and stator. Also make sure that your kill switch is not shorted or grounded out either at the switch or along the wires.

Install a new needle and seat as per manual.

you need to change the fluid and adjust the clutch. There is water etc. in the trans and it effects the clutch.

Old least depletes compared with fuel gasonline. Engine oild should continue to lubrocate unless where drained from compartment. Vehicles usually require much fule than oil. Observe bikes fiud compartments, written details are amde availlable.

The bore has to be measured at a number of places to see if it is out of round 0.01mm or tapered 0.05mm
You will need to take it to an engineering shop that can do the boring, they can measure the piston and bore to determine what oversize it will need.
with only light scratches probably 1 oversize 0.25mm, if it has been bored before the oversize is stamped on the top of the piston. 0.25, 0.50, 0.75
A rough measurement can be done with a feeler gauge, between the piston skirt and bore.
piston clearance for a 125 is about 0.055-0.060mm with a limit of 0.1mm

Thank you for contacting FixYa with your inquiry
Capacity - Transmission Oil Gear Oil (All 125/150 Models) 0.70 Liters (0.74 qt) Engin Oil 15W/50)
Guideline Use High quality 2-stroke engine oil of a well-known brand. KTM recommends Motorex products Su[plier Motorex - Cross Power 2T
This service manual information link might be helpful: should be same for all years. http://www.ktm.com/uploads/tx_ktmproduct/techdocs/6101L0_34254324.pdf.

Flush it with a conditioner and fill properlly

Does it do it at idle,or all revs,does it get worse as revs increase?

Can you please explain what happened a little better?What did you do to check for damage?Testing needs to be more extensive than just observing it while it is sitting still.What you need to do is have someone hold up the bike and push down on the seat with your hands.Look at the suspension mounts.They could have cracked but may not be noticeable until it is stressed upon.Someone else on it and you bouncing it will enable you to examine everything or have them bounce it,whatever it takes.If you have any questions or need more help,just comment here and I will get an autolink to your post and reply ASAP.Greg

.7 liter

Try this web site,...
www.bikebandit.com/

Fitting a new head will not give spluttering in the gears .Your problem will not be anything to do with the mixer screw .check your carb jets for blockage .

if by foamed up you mean its creamy to touch & taken on a greyish colour I would suspect a blowen head gasket

you must first remove engine from the frame. Then remove flywheel,rt hand cover ,clutch, crankshaft gear,head,cylinder,reed cage,shift shaft. Then the crank cases can be split very carefully as transmission may have shims that may come off. If you are unfamiliar withe the 2 stroke motor it is quite a challenge as there are many places that things can be done wrong. Sometimes it is best to take to a professional for this reason.

If you fill it with 0.75 us quarts(about 690 ml) of 20~40 weight ,Shell racing X-40 Recommended that will get you roosting again , john.

Provided you used the correct piston, it could be your ignition timing. You didn't mention anything about changing the jetting in your carb so that should not be a problem unless you changed something else, like the chamber. It could also be your exhaust port contol. This is basically a variable exhaust port and it has to be set up right.

hi buddy are you mixing it correctly with a mixing bottle with 40:1 ratio also on the carb will be a screw mixture screw turn this all the way in and unscrew it 1 1/2 turns out and try this also is there compression get back to me

I would check the work you did on replacing the clutch as the most obvious place to look.

Jy kan die bande 2.3 bar (230 kPa) maak vir asfalt, 1.6 vir offroad, jy sal voel as dit te slap is op asfalt. Moenie veel meer as 2.7bar gaan nie.

Ek het op my XR500 Scrambler die filter elke tweede maand, omtrent elke 4000km, vervang want ek het baie offroad gery.