KTM 2012 250 SX-F Operating instructions

In-Depth Engine and Fuel
System Maintenance and
Repair Manual
2012 KTM 250 SX-F

Jeremy Jonas
December 2, 2013
Denton, TX

iii
Table of Contents
Table of Contents................................................ ii
Introduction ....................................................... 1
Troubleshooting.................................................. 3
Fuel System .................................................... 3
Engine ............................................................ 4
Common Maintenance and Repairs: Fuel System .... 5
Replacing the Fuel Filter.................................... 5
Changing the Fuel Injector ................................ 7
Replacing the ECU...........................................8
Testing the Fuel Pump…………………………………………10
Common Maintenance and Repairs: Engine .......... 11
Checking Valve Clearance……………………………………11
Changing the Piston…………………………………………….13
Checking the Cylinder for Wear and Damage…….18
Checking the Crank Rod Bearings for Wear……….20
Checking the Main Crank Bearings for Wear………21
Checking the Timing…………………………………………….22
Engine Tightening Torques ................................. 23
Bibliography ..................................................... 26
Index…………………………………………………………………..……27

1
Introduction
Congratulations on your purchase of the 2012 KTM
250 SX-F. The purpose of this manual is to assist
you in completing important maintenance and
repairs for your KTM motorcycle. Through following
the original KTM Owners’ Manual and this additional
reference, you will be able to more independently
work your motorcycle. This manual covers two main
sections, Fuel, and Engine. When a problem arises
with your motorcycle, refer to the troubleshooting
section and then look to the suggested instructions
for the diagnosed issue. For maintenance, you
should follow the original maintenance procedures
from the KTM Owners’ Manual. The instructions for
the common Engine and Fuel maintenance that are
not included in the Owners’ Manual can be found in
this Manual.
Note: This manual only covers in-depth Fuel and
Engine work that is not included in the Owner’s
Manual.

Troubleshooting
3
Troubleshooting: Fuel System
Problem
Possible
Cause
Solutions
Bike speeds
up too
slowly or
sputters
when
accelerating
Dirty Fuel Filter
Replace fuel
filter (pg. 4)
Faulty Fuel
Injector
Replace fuel
injector (pg. 7)
Bad Fuel
Empty fuel tank
and re-fill with
new unleaded
ethanol-free
gas.
Loss of fuel
pressure/Bad
fuel pump
Check fuel
hoses for loose
fittings and
possible leaks
Test fuel pump
(pg.10)
ECU Issue
Replace ECU
(pg.8)
Take existing
ECU to KTM
dealership for
re-mapping
Engine
cranks but
does not
start
Bad fuel pump
Check fuel
hoses for loose
fittings and
possible leaks
Test fuel pump
(pg.10)

4
Troubleshooting: Engine
Problem
Possible Cause
Solutions
Engine
Rattling
Improper Valve
Clearance
Adjust
Valves(pg.11)
Engine timing off
Adjust
Timing(pg.23)
Excess Piston
Wear
Replace piston
and rings(pg.13)
Excess Rod
Bearing Wear
Check crank rod
bearings(pg.21)
Loss of
Power
Excess Piston
Wear
Replace piston
and rings(pg.13)
Smoke
coming
out of
exhaust
Damaged
Cylinder
Check and
replace Cylinder,
piston, and rings
(pg.13)
Check oil level
Engine
will
crank
but
won’t
start
Improper Valve
Clearance
Adjust Valves
(pg.11)
Engine timing off
Adjust Timing
(pg.23)
Engine
won’t
turn over
Possible damaged
Piston, Cylinder,
or Crankshaft
Check Piston
Check Cylinder
Check Crank

Common Maintenance and Repairs: Fuel System
5
Replacing the Fuel Filter
Tools needed:
8mm T-handle or socket
Phillips screwdriver
10mm T-handle or socket
Parts needed:
Fuel Filter Part #81207090000
Step 1: Remove the Seat
Using your 8-mm T-handle or socket remove the bolt
under the rear fender as shown in Picture 1, then
remove seat.
Picture 1(Paochow)
Step 2: Remove the Fuel Tank
Using you 8-mm T-handle or socket, remove the bolt
on top of the fuel tank as shown in picture 1.1, and
then remove the 10-mm bolts connecting the
shrouds to the front radiators. Disconnect the
electronic cable on the top of the fuel tank. Then

6
disconnect the fuel cable as in picture 1.2. You can
now remove the fuel tank.
Picture 1.1 (Dirt Rider)
Picture 1.2 (Ntl World)

Common Maintenance and Repairs: Fuel System
7
Step 3: Replace the Fuel Filter
Locate the clamp at the end of the main fuel line
(shown in picture 1.3).
Picture 1.3 (Enduro 360)
Using your Phillips screwdriver, remove part B.
Locate the fuel filter (Part A), and remove it from the
plastic fitting (Part C). Gently place your new fuel
filter into Part C.
Changing the Fuel Injector
Tools Needed
8mm T-handle or socket
10mm T-handle or socket
Phillips Screwdriver
Phillips short socket
Parts Needed
Fuel Injector Part #77141023044
Part
B
Part A
Part C

8
Step 1: Remove Seat and Fuel Tank (pg.5)
Step 2: Remove fuel injector
Using your Phillips screwdriver, remove the two
screws (shown in picture 1.3) holding the fuel
injector in place.
Picture 1.3 (ebay)
After removing the bolts, gently un-plug the injector
and Replace it with the new one.
Replacing the ECU
Tools needed:
8mm T-handle or socket
10 mm T- handle or socket
Parts Needed
Aftermarket ECU/Used ECU(Cannot buy a new
OEM ECU)

Common Maintenance and Repairs: Fuel System
9
Step 1: Remove the seat (pg. 5)
Step 2: Remove the ECU
Locate the ECU (picture 1.4) located behind the fuel
tank. Gently unplug the Main connection and replace
the ECU.
Picture 1.4 (Rubber Side Up)

10
Testing the Fuel Pump
Step 1: Remove Seat (pg. 5)
Step 2: Test Pump
To test the fuel pump, tap the electric start once and
you will hear the pump turning for 3 seconds or
more. If the pump turns for less than 3 seconds,
then it needs to be replaced.

Common Maintenance and Repairs: Engine
11
Checking Valve Clearance
Tools needed
8mm T-handle or socket
10mm T-handle or socket
Feeler Gauge
Parts Needed
Valve Shim Kit
Step 1: Remove the Valve Cover
Using your 10mm socket, remove the three bolts
holding the valve cover in place as shown in picture
1.5. Then remove the Valve cover.
Picture 1.5 (Motorcycle.com)

12
Step 2: Check Valve Clearance
Slide your feeler gauge into the gap between the
valve shim and the rocker arm. The proper valve
clearance for a 2012 KTM 250 SX-F is 18-23
thousands of an inch. If you cannot fit the 18 into
the gap, then you need to put the next size smaller
shim in. If you cannot fit the 23 into the gap, then
you need to increase the valve shim size. Below is a
picture to assist you in the process.
Picture 1.6 (SM Junkie)
Rocker Arm
Valve
Shim

Common Maintenance and Repairs: Engine
13
Changing the Piston
Tools Needed
8mm T-handle or socket
10mm T-handle or socket
30mm deep socket
13mm hex key
15mm deep socket
27mm deep socket
Flathead screwdriver
Parts Needed
2012 KTM 250sx-f Piston Kit (aftermarket or
OEM)
Cylinder Head Gasket Kit (aftermarket or OEM)
Step 1: Remove the Valve Cover (pg. 11)
Step 2: Put the motor on top dead center (TDC)
The first thing you need to do is remove the large
Screw in the center of the stator cover (Picture 1.7).
Picture 1.7 (Dirt Rider)

14
Now that you have removed the bolt, you can begin
turning the motor over until the motor reaches top
dead center. The easiest way to do this is to locate
the two gold marks on the KTM timing gears. When
these marks are facing each other (Picture 1.8), the
Motor is on TDC.
Picture 1.8 (Kevyorks)
Now that the motor is on TDC, we can lock the
crankshaft so that the motor cannot turn while we
are disassembling it. Below the water pump on the
right side of the motor, you will find a bronze hex
screw. Using your 13mm hex key, remove the screw.
Then remove the washer, and put the screw back in.
You may have to turn the motor back and forth a few
times to get it all the way in. This will lock the motor.