KTM 50 SX 2010 Operating instructions

REPAIR MANUAL 2010
50 SX
50 SX Mini
Article no. 3206072en

INTRODUCTION 1
INTRODUCTION
Read this repair manual carefully and thoroughly before beginning work.
Only use ORGINAL KTM SPARE PARTS.
The vehicle will only be able to meet the demands placed on it if the specified service work is performed regularly and properly.
This repair manual was written to correspond to the latest state of this series. We reserve the right to make changes in the interest of
technical advancement without at the same time updating this manual.
We shall not provide a description of general workshop methods. Likewise, safety rules that apply in a workshop are not specified here.
It is assumed that the repair work will be performed by a fully trained mechanic.
All specifications are non-binding. KTM Sportmotorcycle AG specifically reserves the right to modify or delete technical specifica-
tions, prices, colors, forms, materials, services, designs, equipment, etc., without prior notice and without specifying reasons, to adapt
these to local conditions, as well as to stop production of a particular model without prior notice. KTM accepts no liability for delivery
options, deviations from illustrations and descriptions, as well as misprints and other errors. The models portrayed partly contain spe-
cial equipment that does not belong to the regular scope of delivery.
© 2009 by KTM-Sportmotorcycle AG, Mattighofen Austria
All rights reserved
Reproduction, even in part, is permitted only with the express written permission of the copyright owner.
ISO 9001(12 100 6061)
According to the international quality management standard ISO 9001, KTM uses quality assurance processes that lead
to the maximum possible quality of the products.
Issued by: TÜV Management Service
KTM-Sportmotorcycle AG
5230 Mattighofen, Austria

CONTENTS 2
CONTENTS
MEANS OF REPRESENTATION ............................................ 5
IMPORTANT NOTES............................................................ 6
MOTORCYCLE..................................................................... 7
Jacking up the motorcycle................................................ 7
Removing the motorcycle from the work stand.................... 7
Starting .......................................................................... 7
Vehicle level ................................................................... 8
01/FORK, TRIPLE CLAMP.................................................... 9
Cleaning dust boots of fork legs ........................................ 9
Removing the fork legs..................................................... 9
Installing the fork legs ................................................... 10
Servicing fork................................................................ 10
Disassembling the fork legs ............................................ 11
Checking the fork legs.................................................... 12
Assembling the fork legs ................................................ 13
Adjusting the fork overhang ............................................ 14
Removing the lower triple clamp ..................................... 15
Installing the lower triple clamp...................................... 16
Greasing the steering head bearing.................................. 17
Checking play of steering head bearing............................ 18
Adjusting the play of the steering head bearing ................ 18
02/HANDLEBAR, CONTROLS AND INSTRUMENTS.............. 20
Checking the play in the throttle cable............................. 20
Adjusting the play in the throttle cable ............................ 20
Handlebar position ........................................................ 20
Adjusting handlebar position .......................................... 20
04/SHOCK ABSORBER, SWINGARM................................... 22
Adjusting the rebound damping of the shock absorber....... 22
Measuring rear wheel sag unloaded ................................. 22
Checking the static sag of the shock absorber .................. 22
Checking the riding sag of the shock absorber .................. 23
Adjusting the spring preload of the shock absorber ........... 23
Adjusting the riding sag ................................................. 24
Removing the shock absorber ......................................... 24
Installing shock absorber................................................ 24
Adjusting seat height ..................................................... 25
Servicing shock absorber................................................ 25
Removing the spring ...................................................... 25
Disassembling the damper ............................................. 26
Disassembling the piston rod.......................................... 27
Removing the heim joint ................................................ 28
Checking the damper..................................................... 29
Installing the heim joint ................................................. 30
Assembling the piston rod .............................................. 31
Assembling the damper (50 SX)...................................... 32
Assembling the damper (50 SX Mini) .............................. 33
Filling the damper with nitrogen ..................................... 34
Installing the spring (50 SX)........................................... 35
Installing the spring (50 SX Mini) ................................... 36
05/EXHAUST .................................................................... 38
Removing the exhaust manifold ...................................... 38
Installing the exhaust manifold ....................................... 38
Removing main silencer ................................................. 38
Installing the main silencer ............................................ 39
Removing the glass fiber yarn filling of the main
silencer ........................................................................ 39
Installing the glass fiber yarn filling of the main silencer ... 40
06/AIR FILTER.................................................................. 41
Removing the air filter ................................................... 41
Installing the air filter .................................................... 41
Cleaning air filter........................................................... 41
07/FUEL TANK, SEAT, TRIM.............................................. 42
Removing the seat......................................................... 42
Mounting the seat ......................................................... 42
Removing the fuel tank .................................................. 42
Installing the fuel tank................................................... 43
08/MASK, FENDER ........................................................... 44
Dismounting the front fender.......................................... 44
Installing the front fender............................................... 44
Dismounting the start number plate ................................ 44
Installing the start number plate ..................................... 44
09/FRONT WHEEL ............................................................ 46
Removing front wheel .................................................... 46
Installing the front wheel................................................ 46
Checking the tire condition............................................. 47
Checking tire air pressure............................................... 47
Checking brake discs ..................................................... 47
Checking spoke tension.................................................. 48
10/REAR WHEEL .............................................................. 49
Removing rear wheel...................................................... 49
Installing the rear wheel................................................. 49
Checking chain dirt ....................................................... 49
Cleaning the chain......................................................... 50
Checking the chain tension ............................................ 50
Checking the chain tension - installing rear wheel............. 51
Checking rear sprocket / engine sprocket for wear ............. 51
Adjusting chain tension.................................................. 51
Adjusting chain tension - after checking .......................... 52
Adjusting chain tension - installing rear wheel.................. 52
Adjusting the chain guide............................................... 52
13/BRAKE SYSTEM........................................................... 53
Checking the play of the hand brake lever........................ 53
Adjusting the play of the hand brake lever........................ 53
Adjusting the basic position of the hand brake lever.......... 53
Checking the front brake fluid level ................................. 53
Adding front brake fluid ................................................. 54
Changing the front brake fluid ........................................ 55
Checking the front brake linings...................................... 56
Removing front brake linings .......................................... 56
Installing the front brake linings ..................................... 56
Changing the front brake linings ..................................... 57
Checking the free travel of the foot brake lever ................. 58
Adjusting the free travel of the foot brake lever................. 58
Adjusting the basic position of the foot brake lever ........... 58
Checking rear brake fluid level........................................ 59
Adding rear brake fluid .................................................. 59
Changing the rear brake fluid.......................................... 60
Checking the rear brake linings....................................... 61
Removing rear brake linings............................................ 61
Installing the rear brake linings....................................... 62
Changing the rear brake linings....................................... 62
30/ENGINE....................................................................... 64
Removing the engine ..................................................... 64
Installing the engine ...................................................... 65
30/DISASSEMBLING THE ENGINE..................................... 68
Clamping the engine into the engine work stand............... 68
Pulling off the spark plug connector ................................ 68
Draining the gear oil ...................................................... 68
Removing the cylinder head............................................ 68
Removing the cylinder ................................................... 69
Removing the piston ...................................................... 69
Removing the oil pump (50 SX Mini)............................... 69

CONTENTS 3
Removing the alternator cover......................................... 69
Removing the ignition coil, intake flange, and reed valve
housing ........................................................................ 70
Removing the oil pump drive gear (50 SX Mini)................ 70
Removing the stator....................................................... 70
Removing the rotor ........................................................ 70
Removing the engine sprocket ........................................ 71
Removing the kickstarter................................................ 72
Removing the water pump cover ..................................... 72
Removing the outer clutch cover ..................................... 72
Removing the clutch cover ............................................. 72
Removing the clutch drum ............................................. 72
Removing the kickstarter gear......................................... 73
Removing the kickstarter idler shaft ................................ 73
Loosening the nut of the primary gear.............................. 73
Removing the centrifugal force clutch ............................. 73
Removing the kickstarter shaft........................................ 73
Removing the clutch bearing .......................................... 74
Removing the primary gear ............................................. 74
Removing the left engine case ........................................ 74
Removing the transmission shafts ................................... 75
Removing the crankshaft................................................ 75
30/ENGINE - WORK ON INDIVIDUAL PARTS....................... 76
Work on the right section of the engine case .................... 76
Work on the left section of the engine case ...................... 76
Changing the conrod bearing .......................................... 77
Checking the crankshaft run-out on the bearing pin .......... 78
Removing the water pump.............................................. 78
Installing the water pump............................................... 79
Changing the shaft seal ring of the kick starter ................. 79
Dismantling centrifugal clutch ........................................ 80
Assembling centrifugal clutch......................................... 80
Checking/measuring clutch............................................. 81
Checking/measuring the cylinder..................................... 81
Checking/measuring the piston ....................................... 82
Determining piston/cylinder mounting clearance............... 82
Checking the piston ring end gap .................................... 83
Checking reed valve housing, diaphragm and intake
flange........................................................................... 83
30/ASSEMBLING THE ENGINE .......................................... 84
Installing the crankshaft................................................. 84
Installing the transmission shafts.................................... 84
Installing the left engine case......................................... 84
Installing the primary gear.............................................. 85
Installing the clutch bearing ........................................... 85
Installing the kickstarter shaft ........................................ 85
Installing the centrifugal force clutch .............................. 85
Tightening the nut of the primary gear............................. 85
Installing the kickstarter idler shaft ................................. 86
Installing the kickstarter gear.......................................... 86
Installing the clutch drum .............................................. 86
Installing the clutch cover .............................................. 86
Installing the outer clutch cover...................................... 87
Mounting the water pump cover ...................................... 87
Installing the kickstarter................................................. 87
Installing the engine sprocket ......................................... 87
Installing the rotor......................................................... 88
Installing the stator ....................................................... 89
Adjusting the stator/rotor distance................................... 89
Installing the oil pump drive gear (50 SX Mini)................. 89
Installing the reed valve housing, ignition coil, and intake
flange........................................................................... 89
Installing the alternator cover ......................................... 90
Installing the oil pumps (50 SX Mini) .............................. 90
Installing the piston....................................................... 90
Installing the cylinder .................................................... 91
Checking the X-distance................................................. 91
Setting the X-distance.................................................... 92
Installing the cylinder head ............................................ 92
Installing the oil drain plug............................................. 92
Refilling with gear oil..................................................... 93
Mounting the spark plug connector ................................. 93
Removing the engine from the universal mounting rack ..... 93
31/CARBURETOR ............................................................. 94
Removing the carburetor (50 SX) .................................... 94
Removing the carburetor (50 SX Mini)............................. 95
Installing the carburetor (50 SX)..................................... 96
Installing the carburetor (50 SX Mini).............................. 97
Checking/setting the carburetor components (50 SX) ........ 98
Checking/setting the carburetor components
(50 SX Mini)................................................................. 99
Disassembling the carburetor (50 SX).............................. 99
Disassembling the carburetor (50 SX Mini) .................... 101
Assembling the carburetor (50 SX)................................ 102
Assembling the carburetor (50 SX Mini) ........................ 104
Checking the choke slide (50 SX).................................. 105
Checking the choke slide (50 SX Mini) .......................... 105
Checking the throttle slide (50 SX)................................ 106
Checking the throttle slide (50 SX Mini) ........................ 106
Checking the jet needle................................................ 106
Checking the float needle valve..................................... 106
Checking/setting the float level (50 SX) ......................... 107
Carburetor - adjusting idle speed (50 SX)....................... 107
Carburetor - adjusting idle speed (50 SX Mini) ............... 108
32/CLUTCH .................................................................... 109
Removing the centrifugal force clutch ........................... 109
Fitting centrifugal force clutch...................................... 109
Checking clutch engagement speed............................... 110
Adjust the clutch engagement speed ............................. 110
35/WATER PUMP, COOLING SYSTEM .............................. 112
Draining the coolant .................................................... 112
Refilling coolant .......................................................... 112
Checking the coolant level............................................ 113
Checking the antifreeze and coolant level ...................... 113
38/LUBRICATION SYSTEM .............................................. 115
Changing the gear oil ................................................... 115
Draining the gear oil .................................................... 115
Filling up with gear oil ................................................. 115
Checking the gear oil level............................................ 116
Adding gear oil............................................................ 116
Filling up with oil (50 SX Mini)..................................... 117
Bleeding oil pump (50 SX Mini).................................... 117
39/IGNITION SYSTEM ..................................................... 119
Checking the ignition system ........................................ 119
Checking the spark plug connector................................ 119
Checking the ignition coil............................................. 119
Checking the kill switch ............................................... 120
Checking the alternator ................................................ 120
TROUBLESHOOTING....................................................... 121
TECHNICAL DATA - ENGINE............................................ 123
Capacity - gear oil........................................................ 123
Capacity - coolant........................................................ 123
TECHNICAL DATA - TOLERANCE, WEAR LIMITS OF
ENGINE ......................................................................... 124

CONTENTS 4
TECHNICAL DATA - ENGINE TIGHTENING TORQUES........ 125
TECHNICAL DATA - CARBURETOR................................... 126
50 SX......................................................................... 126
50 SX Mini ................................................................. 126
TECHNICAL DATA - CHASSIS .......................................... 127
Tires .......................................................................... 127
Capacity - fuel............................................................. 128
TECHNICAL DATA - FORK................................................ 129
50 SX......................................................................... 129
50 SX Mini ................................................................. 129
TECHNICAL DATA - SHOCK ABSORBER ........................... 130
50 SX......................................................................... 130
50 SX Mini ................................................................. 130
TECHNICAL DATA - TIGHTENING TORQUES FOR
CHASSIS ........................................................................ 131
CLEANING/CONSERVATION............................................. 132
Cleaning motorcycle .................................................... 132
STORAGE ....................................................................... 133
Storage....................................................................... 133
Putting into operation after storage ............................... 133
SERVICE SCHEDULE....................................................... 134
Important maintenance work that must be done in an
authorized KTM workshop ............................................ 134
Important maintenance work that must be done in an
authorized KTM workshop (as additional order)............... 134
WIRING DIAGRAM .......................................................... 136
Wiring diagram............................................................ 136
SUBSTANCES................................................................. 138
AUXILIARY SUBSTANCES................................................ 140
SPECIAL TOOLS.............................................................. 142
STANDARDS................................................................... 149
INDEX ............................................................................ 150

MEANS OF REPRESENTATION 5
Symbols used
The symbols used are explained in the following.
Indicates an expected reaction (e.g. of a work step or a function).
Indicates an unexpected reaction (e.g. of a work step or a function).
All work marked with this symbol requires specialist knowledge and technical understanding. In the interest of
your own safety, have these jobs done in an authorized KTM workshop! There, your motorcycle will be serviced
optimally by specially trained experts using the specialist tools required.
Identifies a page reference (more information is provided on the specified page).
Formats used
The typographical and other formats used are explained in the following.
Proper name Identifies a proper name.
Name®Identifies a protected name.
Brand™ Identifies a brand in merchandise traffic.

IMPORTANT NOTES 6
Warranty
The work prescribed in the service schedule must be carried out in an authorized KTM workshop only and confirmed in the customer's
service record, since otherwise no warranty claims will be honored. No warranty claims can be honored for damage resulting from
manipulations and/or alterations to the vehicle.
Fuel, oils, etc.
You should use the fuels, oils, and greases according to specifications as listed in the owner's manual.
Spare parts, accessories
Only use spare parts and accessories approved and/or recommended by KTM. KTM accepts no liability for other products and any
resulting damage or loss.
You will find the current KTM PowerParts for your vehicle on the KTM website.
International KTM Website: http://www.ktm.com
Work rules
Special tools are needed for certain tasks. They are not included with the vehicle but can be ordered under the number in parenthe-
ses. Ex.: bearing puller (15112017000)
During assembly, non-reusable parts (e.g. self-locking screws and nuts, seals, seal rings, O-rings, pins, lock washers) must be replaced
by new parts.
If a thread locker is used for the screw connections (e.g. Loctite®), follow the specific manufacturer instructions regarding its use.
Parts that are to be reused after disassembly must be cleaned and checked for damage and wear. Change damaged or worn parts.
After repair and maintenance, ensure that the vehicle is roadworthy.
Notes/warnings
Pay close attention to the notes/warnings.
Info
Various information and warning labels are affixed to the vehicle. Do not remove information/warning labels. If they are miss-
ing, you or others may not recognize potential hazards and may therefore be injured.
Grades of risks
Danger
Identifies a danger that will immediately and invariably lead to fatal or serious permanent injury if the appropriate measures
are not taken.
Warning
Identifies a danger that is likely to lead to fatal or serious injury if the appropriate measures are not taken.
Note
Identifies a danger that will lead to considerable machine and material damage if the appropriate measures are not taken.
Warning
Identifies a danger that will lead to environmental damage if the appropriate measures are not taken.
Repair manual
–It is important that you read this repair manual carefully and thoroughly before beginning work. It contains useful information and
tips that will help you repair and service your motorcycle.
–This manual assumes that the necessary special KTM tools and workplace and workshop equipment are available.

MOTORCYCLE 7
3.1Jacking up the motorcycle
700475-01
Note
Danger of damage The parked vehicle may roll away or fall over.
–Always place the vehicle on a firm and even surface.
–Jack up the motorcycle underneath the engine.
Work stand (54829055000) ( p. 145)
–Secure the motorcycle against falling over.
3.2Removing the motorcycle from the work stand
Note
Danger of damage The parked vehicle may roll away or fall over.
–Always place the vehicle on a firm and even surface.
–Remove the motorcycle from the work stand.
–Remove the work stand.
3.3Starting
Danger
Danger of poisoning Exhaust gases are poisonous and inhaling them may result in unconsciousness and/or death.
–When running the engine, always make sure there is sufficient ventilation, and do not start or run the engine in an enclosed
space without an effective exhaust extraction system.
Note
Engine failure High engine speeds in cold engines have a negative effect on the service life of the engine.
–Always warm up the engine at low engine speeds.
Info
If the motorcycle is unwilling to start, the cause can be old fuel in the float chamber. The flammable elements of the fuel
evaporate after a long time of standing.
If the float chamber is filled with fresh fuel, the engine starts immediately.
–Turn the knurled screw on the fuel tap all the way counterclockwise.
Fuel can flow from the fuel tank to the carburetor.
–Remove the motorcycle from the stand.
The engine is cold
(50 SX)
–Pull the choke knob fully out and turn it by max. ¼ turn.
(50 SX Mini)
–Push the choke lever up all the way.
–Forcefully step on the kickstarter, pushing it all the way forward.
Info
Do not open the throttle.

MOTORCYCLE 8
3.4Vehicle level
Warning
Danger of accidents Modifications to the suspension settings can seriously alter
the vehicle's ride behavior.
–Following modifications, ride slowly at first to get the feel of the new ride
behavior.
The vehicle level can be adjusted at the front by means of the clamping of the fork legs
and at the rear by means of the positioning of the shock absorber.
700523-10
The fork overhang can be individually adjusted to the size of the child. In the lower
position (standard), the fork is completely pushed through. In the higher position ,
the cone is flush with the upper triple clamp.
Fork overhang over the
upper triple clamp
10… 17 mm (0.39… 0.67 in)
700521-11
The seat height can be individually adjusted to the size of the child. The shock
absorber can be mounted at two different holes in the frame.
Difference between low 
(standard) and high seat
position
25 mm (0.98 in)