KTM 125 SX 2019 User Manual

19 TROUBLESHOOTING
116
Faults Possible cause Action
Engine stalls or is popping into
the carburetor
Engine takes in bad air – Check the intake flange and carburetor
for tightness.
The connector or ignition coil is
loose or oxidized
– Clean the connector and treat it with
contact spray.
Engine overheats Too little coolant in cooling sys-
tem
– Check the cooling system for leakage.
– Check the coolant level. ( p. 97)
Too little air stream –
Switch off engine when stationary.
Radiator fins very dirty – Clean the radiator fins.
Foam formation in cooling sys-
tem
– Drain the coolant. ( p. 98)
– Refill with coolant. ( p. 99)
Damaged cylinder head or
cylinder head gasket
– Check the cylinder head and cylinder
head gasket.
Bent radiator hose – Change the radiator hose.
White smoke emission (steam
in exhaust gas)
Damaged cylinder head or
cylinder head gasket
– Check the cylinder head and cylinder
head gasket.
Gear oil exits at the vent hose Too much gear oil added – Check the gear oil level. ( p. 108)
Water in the gear oil Damaged shaft seal ring or
water pump
– Check the shaft seal ring and water
pump.

KTM 125 SX 2019 Specifications

General

Displacement	124.8 cm³
Starter	Kickstarter
Transmission	6-speed
Fuel System	Mikuni TMX 38
Front Brake	Disc brake
Rear Brake	Disc brake
Ground Clearance	375 mm
Seat Height	950 mm
EMS	Kokusan
Engine Type	1-cylinder, 2-stroke
Bore x Stroke	54 mm x 54.5 mm
Rear Suspension	WP shock absorber with linkage
Fuel Tank Capacity	7.5 l
Clutch	Wet, multi-disc clutch, Brembo hydraulics
Frame Design	Central tube frame made of chrome molybdenum steel