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