20 Most Recent 2005 KTM SX 125 Questions & Answers

not sure bout that bike specificaly, probly there is a spring on the gearshift shaft , or something to return the lever and shift drum back whenever actuated. no matter what it is, you gotta split the cases to fix it .

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Place the bike on a suitable stand, undo the wheel spindle, remove the bolts securing the lower chain guide as the bolts reduce clearence, support the wheel by placing a block of wood or similar under the wheel, remove the wheel spindle along with the addjuster blocks on the spindle, now push the wheel forward and remove the chain from the sprocket by

Shift forks are bent or shift rod is bent.
Bent forks or arm won't allow the tranny gears to slide into position.
Must be taken apart, to correctly diagnois,

When you shift with your foot, the shift forks slide on the arm.
If its not going, one of the two or both are bent.

It's a special made joint and not actually a regular bearing, so you won't be able to find a traditional bearing number. KTM or the mc aftermarket is the only place to get them.


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2250+ or - 250 is 2k to 2.5k so best to try on the 20k range.

it sounds as though the selector forks in the g-box are worn.common on competition bikes . But before you go to any expence, carefully inspect the gear linkage, did it happen after a off.look for bent linkage and gear lever, also has it been put back correctly double check is it right way up.and that gear lever position is set correctly for your foot.

Sounds like a major broken bike!
What i do, is remove the gear that runs between the crank, and clutch to see what end is frozen, the transmission, or the engine.
You can also take off the exhaust pipe and look in the hole for damage.

you are running to rich by the sounds of it ..dave

Remove the water trap bowl at the bottom of the petcock, (gas valve). Any water or trash in the bowl? Drain a cup of gas from the tank. Any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ).

Drain the carburetor. There may be a screw on the lower side of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. Install a new stock NGK spark plug and try to start the engine. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.

Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Remove the two screws on the outside throat of the carb and spray into the screw holes as well.
< < READ CLOSELY > >
Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward. Put the rest of the carb back together, clean the air filter and install the carb. Be sure the bolts are tight. Let the float bowl fill then start the engine. Set the idle speed with the idle screw, (sticks out from side of carb perpendicular to the carb throat).

If you are smoking that badly, loose the gas in the tank and start fresh with a 32/1 gas/oil mix. That equals 4 ounces of TWO STROKE OIL to one gallon of gas. Do NOT use motor oil in the gas. It may continue to smoke for awhile, until it rids it'self of built up oil in the crankcase.

On the clutch, be sure the oil level in the gearbox is correct. This is where 10w40 motor oil goes. Check the clutch cable linkages. One at the clutch lever and possibly one at the motor. You should have about 1/4" play in the clutch handle before the lever starts actually pulling the clutch.

You can download a free PDF service manual from this site > >
http://www.carlsalter.com/motorcycle-manuals.asp I checked and your manual is on the list.

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Hi, Well that is one way to look at it. Since you don't indicate the premix, the best advice I can give you is that the oil in the mixture is indeed not burning, the easiest fix being to change your premix to include less oil. There are other fixes, hotter plug, higher octane but until you ride and get comfortable with this bike, either let it drip a little or change the mix for now and change it as needed as you get used to it. Good Luck to you, this should Fixsya!

Give a better description and/or some pics so I can understand what you are experiencing bud.

is there a spark at the ht lead cap , remove cap and test again ? plug or cap can fail !

release water undo hoses remove holding bolts

You will need to slightly loosen the line where it goes into the master cylinder,...then squeeze the lever and hold it in...fluid should come out. While holding lever in,re-tighten bolt. You should get a lil bit of lever feel now. Making sure there is fluid in the resrvoir,...squeeze lever multiple times,and hold it in,....loosen the banjo bolt again,...slowly,..untill fluid rushes out. Then,..while holding lever in,retighten banjo bolt again. Check fluid,...then pump the lever multiple times again,and you should be getting some good lever feel now. After this,you may need to bleed the air out at the bleeder a couple times till alll the air is out.

Get new engine oil and ad a little bit more 2Stroke oil with petrol and make sure your water is full ?

Thank you for contacting FixYa with your inquiry. I have been going
over some of the older help requests that have been archieved and
trying to provide solutions for those that didn't get answered. Hope
this information helps.

You might have bent shifting forks or the dogs on the gears are worn. That would be a case split and Removal and Repair of bad parts.

TRY THIS FIRST:
Work on your shifting technique. When you want to shift from 1st to second apply up pressure with your toe and roll the throttle off and let it pop into gear. Don't use the clutch other than for starting or a few suituations where you need to idle while in gear. You might not be allowing the transmision to pull 2nd gear all the way in and it drops back to neutral.

Hope this helps.

Thank you for contacting FixYa with your inquiry. I have been going
over some of the older help requests that have been archieved and
trying to provide solutions for those that didn't get answered. Hope
this information helps.

Start in the middle. Check you spark plug it should be a nice cocoa brown color. If its stumbling and not running correctly then lower it 1 notch (This Raises the Needle alowing more fuel) if the plug is fouled and wet then your over fueling in the middle to high end so raise the circlip (Lowering the needle - reducing fuel) adjust accordingly using your spark plug color as the guage.

The Main Jet determines fuel mix at top speed and the needle fits into it's oriface regulating speed depending on throttle position. You may have to to up or down a size depending on you altitude.

TF