KTM 125 SX 2010 User Manual (English)

Questions and Answers:

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Michelle ClaytonAug 15, 2025
Why does my KTM 125 SX 2010 engine have too little power?
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  lauraromanAug 15, 2025
  If your KTM Motorcycle engine has too little power, the possible causes are: the fuel feed is interrupted, the air filter is very dirty, the exhaust system is leaky or deformed, there is too little glass fiber yarn filling in the main silencer, there is a fault in the ignition system, or the diaphragm or reed valve housing is damaged. To solve this, check the fuel tank breather, clean the fuel tap, and check/set the carburetor components. Clean the air filter. Inspect the exhaust system for damage and replace the glass fiber yarn filling of the main silencer. Check the ignition system. Finally, inspect the diaphragm and reed valve housing.
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Chad HillAug 18, 2025
Why is my KTM Motorcycle engine overheating?
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  Mariah BairdAug 18, 2025
  If your KTM Motorcycle engine is overheating, the problem could be caused by several factors. The radiator fins may be very dirty, or there could be foam formation in the cooling system. A damaged cylinder head or cylinder head gasket, a bent radiator hose, or an incorrect ignition point due to a loose stator could also be responsible. To address these issues, clean the radiator fins. If there's foam in the cooling system, drain and refill it with coolant. Inspect the cylinder head and cylinder head gasket for damage. Replace any bent radiator hoses and adjust the ignition if the stator is loose.
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Oscar McguireAug 21, 2025
How to fix KTM 125 SX 2010 engine that does not speed up?
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  Brandon PerezAug 21, 2025
  If your KTM Motorcycle engine does not speed up, it could be due to a carburetor running over because the float needle is dirty or worn, loose carburetor jets, or a fault in the ignition system. To resolve this, check and set the carburetor components and inspect the ignition system.
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Jason JonesAug 25, 2025
Why is gear oil exiting at the vent hose of my KTM 125 SX 2010 Motorcycle?
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  Keith DeleonAug 26, 2025
  If gear oil is exiting at the vent hose of your KTM Motorcycle, it is likely because too much gear oil was added. Check the gear oil level.
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Courtney WalterAug 28, 2025
Why is there water in the gear oil of my KTM 125 SX 2010 Motorcycle?
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  Jason BrownAug 28, 2025
  If there's water in the gear oil of your KTM Motorcycle, it could be due to a damaged shaft seal ring or water pump. You should check the shaft seal ring and water pump.
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David FergusonAug 31, 2025
What to do if my KTM 125 SX 2010 engine turns but does not start?
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  michellesanchezAug 31, 2025
  If your KTM Motorcycle engine turns but doesn't start, there are several potential causes. You may need to review the engine starting procedure. If the motorcycle has been stored for a long time, the carburetor float chamber may contain old fuel and should be emptied. Check for any interruptions to the fuel feed, or if the engine is flooded, clean and dry the spark plug, replacing it if necessary. Also, ensure the spark plug gap is correctly adjusted. If these steps don't resolve the issue, the ignition system may be faulty, or there might be a short circuit; in this case, check the short circuit button. Clean any loose or oxidized socket connectors or the ignition coil, and check for water in the carburetor or blocked jets.
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Jason McgeeSep 4, 2025
What to do if my KTM 125 SX 2010 engine stalls or is popping into the carburetor?
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  Richard BairdSep 4, 2025
  If your KTM Motorcycle engine stalls or pops into the carburetor, it could be due to several reasons. Make sure the fuel tap is in the ON position and refuel if necessary. Check the intake flange and carburetor for tightness, as the engine might be taking in bad air. Clean any loose or oxidized socket connectors and treat them with contact spray. Also, ensure there's enough coolant in the cooling system by checking for leaks and verifying the coolant level.
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Joe Gibson MDSep 7, 2025
Why KTM 125 SX 2010 engine has no idle?
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  Andrea PowellSep 7, 2025
  If your KTM Motorcycle engine has no idle, it could be due to a blocked idling jet, distorted adjusting screws on the carburetor, a defective spark plug, or a defective ignition system. To address this, check and set the carburetor components. Adjust the idle speed of the carburetor. Change the spark plug. Check the ignition coil and the spark plug connector.
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Nicole GarciaSep 12, 2025
What does it mean if my KTM Motorcycle emits white smoke?
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  Whitney HenrySep 12, 2025
  If your KTM Motorcycle is emitting white smoke, it may be caused by a damaged cylinder head or cylinder head gasket. In this case, check the cylinder head or cylinder head gasket.

KTM 125 SX 2010 Specifications

General

Engine Type	Single cylinder, 2-stroke
Displacement	124.8 cc
Bore x Stroke	54.0 mm x 54.5 mm
Transmission	6-speed
Fuel System	Carburetor
Ignition	CDI
Frame	Chromium molybdenum steel
Front Brake	Disc brake
Rear Brake	Disc brake
Starter	Kick starter
Fuel Tank Capacity	7.5 liters (2.0 gallons)
Compression Ratio	Not available
Front Suspension	USD fork, 48 mm
Rear Suspension	Monoshock