KTM EXC Operating instructions

Repair manual KTM 250 / 300 / 380 Art No 3206004 -E
250/300/380 SX,MXC,EXC
REPAIR MANUAL
ENGINE
KTM SPORTMOTORCYCLE AG
5230 Mattighofen
Austria
www.ktm.at

REPAIR
MANUAL
ENGINE
250 - 380
SX,MXC,EXC

1SERVICE-INFORMATIONS
2GENERAL INFORMATION
3REMOVING AND REFITTING ENGINE
4DISASSEMBLING THE ENGINE
5 SERVICING ON INDIVIDUAL COMPONENTS
6ASSEMBLING THE ENGINE
7ELECTRICAL
8TROUBLE SHOOTING
9TECHNICAL SPECIFICATIONS
10 PERIODIC MAINTENANCE SCHEDULE
11 WIRING DIAGRAMS
12
13
14
15
16

Repair manual KTM 250 / 300 / 380 Art No 3206004 -E
Remove page (s) Replace by page (s) Insert page (s) after page
2-1 to 2-4 2-1C to 2-6C
3-4 3-4C
4-1 to 4-9 4-1C to 4-8C
5-1 5-1C
5-4 5-4C / 5-5C
5-13 to 5-14 5-13C to 5-14C
7-1 7-1C 7-5C to 7-10C
9-1 9-1C 9-37C to 9-42C
10-1 10-1C 10-6C to 10-8C
11-1 11-1C 11-14C to 11-16C
IMPORTANT INFORMATION/UPDATING INSTRUCTIONS
To be able to continue using the existing loose-leaf repair instructions, simply print the following
pages and insert them in the existing repair instructions:
14-20, 26, 28-36, 37, 41, 42, 50, 51, 67, 72-77, 83, 121-126, 127, 134-136,
137, 151-153
KTM REPAIR MANUAL IN LOOSE-LEAF FORM
STORING THE REPAIR MANUAL IN THE BINDER
–Put the index into the binder.
–Put the front page of the repair manual (210x297 mm) into the transparent pocket provided for
this purpose on the outside of the binder.
–Put the spine label (170x45 mm) into the transparent pocket provided for this purpose on the
spine of the binder.
–Put the summary list of contents (150x297 mm) into the transparent pocket provided for this
purpose on the inside of the binder or insert this page on the beginning of the manual.
–Then insert the individual chapters of the manual between the sheets of the index according to
the page number printed in the right bottom corner of each page.
Example: page no. 3-5 3 = chapter 3 5 = page 5
All pages with a page number that begins with the digit 3, for example, must be put under the
index heading „Chapter 3“.
–Index sheets that have not been marked with a certain chapter are for your personal convenience.
The respective headings can be entered in the list of contents.

EXPLANATION - UPDATING
Edition 11/2002
Repair manual KTM 250 / 300 / 380 Art No 3206004 -E
3.205.63-E Repair Manual 250 / 300 / 380 SX, MXC, EXC
Basicversion Modelyear 1999
(Engine number with first digit “9“)
11/1998
3.205.87-E Updating of Rep.Manual 3.205.63-E
Modelyear 2000
(Engine number with first digit “0“)
2/2000
3.210.02-E Updating of Rep.Manual 3.205.63-E
Modelyear 2001/2002
(Engine number with first digit “1“)
(Engine number with first digit “2“)
3/2001
3.206.004-E Updating of Rep.Manual 3.205.63-E
Modelyear 2003
(Engine number with first digit “3“)
11/2002
Modification / Updating:
Technical Specification,
Periodic Maintenance Schedule, Wiring Diagrams

INTRODUCTION
This repair manual offers extensiv repair-instructions and is an up-to-date version that describes the
latest models of the series. However, the right to modifications in the interest of technical
improvement is reserved without updating the current issue of this manual.
A description of general working modes common in work shops has not been included. Safety rules
common in the work shop have also not been listed. We take it for granted that the repairs are made
by qualified profesionally trained mechanics.
Read through the repair manual before beginning with the repair work.

WARNING

STRICT COMPLIANCE WITH THESE INSTRUCTIONS IS
ESSENTIAL TO AVOID DANGER TO LIFE AND LIMB.
!
CAUTION
!
NON-COMPLIANCE WITH THESE INSTRUCTIONS CAN LEAD TO
DAMAGE OF MOTORCYCLE COMPONENTS OR RENDER
MOTORCYCLES UNFIT FOR TRAFFIC !
„NOTE” POINTS OUT USEFUL TIPS.
Use only ORIGINAL KTM SPARE PARTS when replacing parts.
The KTM high performance engine is only able to meet user expectations if the maintenance work is
performed regularly and professionally.
KTM Austria’s certificate of achievement for its quality system ISO 9001 is the beginning of an on
going total reengineered quality plan for a brighter tomorrow.
KTM Sportmotorcycle AG
5230 Mattighofen, Austria
All design and assembly modification rights reserved.
C by KTM SPORTMOTORCYCLE AG, AUSTRIA All rights reserved

REPLY FAX FOR REPAIR MANUALS
We have made every effort to make our repair manuals as accurate as possible but it is always possible for
a mistake or two to creep in.
To keep improving the quality of our repair manuals, we request mechanics and shop foremen to assist us
as follows:
If you find any errors or inaccuracies in one of our repair manual – whether these are technical errors,
incorrect or unclear repair procedures, tool problems, missing technical data or torques, inaccurate or
incorrect translations or wording, etc. – please enter the error(s) in the table below and fax the completed
form to us at 0043/7742/6000/5349.
NOTE to table:
–Enter the complete item no. for the repair manual in column 1 (e.g.: 3.210.66-E).
You will find the number on the cover page or in the left margin on each right page of the manual.
–Enter the corresponding page number in the repair manual (e.g.: 5-7c) in column 2.
–Enter the current text (inaccurate or incomplete) in column 3 by quoting or describing the respective
passage of the text. If your text deviates from the text contained in the repair manual, please write your
text in German or English if possible.
–Enter the correct text in column 4.
Your corrections will be reviewed and incorporated in the next issue of our repair manual.
Item no. of repair manual Page Current text Correct text
Additional suggestions, requests or comments on our Repair Manuals (in German or English):
Name mechanic/shop foreman Company/work shop

Repair manual 250 / 300 / 380 Art Nr 3206004 -E
OPERATING RANGES OF THE CARBURETOR . . . . . . . . . . . . . . . . . . .2-2
CARBURETOR ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3
CHECKING OF THE SETTING OF THE TVC SYSTEM . . . . . . . . . . . . . .2-4
BLEEDING OF THE HYDRAULIC CLUTCH . . . . . . . . . . . . . . . . . . . . .2-4
SPECIAL TOOLS - ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6
STORAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6
INDEX
2-1C
GENERAL INFORMATION 2

Repair manual KTM 250 / 300 / 380 Art No 3206004 -E
2-2C
main jet
jet needle
jet needle
air control screw
idle adjusting screw
idle jet
throttle valve
Idling range A
Operation with closed throttle valve. This range is influenced by the position of the air control screw 1and the idle adjusting screw
2. Only make adjustments when the engine is hot.
To this end, slightly increase the idling speed of the engine by means of the idle adjusting screw. Turning it clockwise produces a
higher idling speed and turning the screw counterclockwise produces a lower idling speed. Create a round and stable engine speed
using the air control screw (basic position of the air control screw = open by 1.5 turns). Then adjust to the normal idling speed by
means of the idle adjusting screw.
Opening up B
Engine behavior when the throttle opens. The idle jet and the shape of the throttle valve influences this range. If, despite good
idling-speed and part-throttle setting, the engine sputters and smokes when the throttle is fully opened and develops its full power
not smoothly but suddenly at high engine speeds, the mixture to the carburetor will be too rich, the fuel level too high or the float
needle is leaking.
Part-throttle range C
Operation with partly open throttle valve. This range is only influenced by the jet needle (shape and position). The optimum
part-throttle setting is controlled by the idling setting in the lower range and by the main jet in the upper range. If the engine runs
on a four-stroke cycle or with reduced power when it is accelerated with the throttle partly open, the jet needle must be lowered by
one notch. If then the engine pings, especially when accelerating under full power at maximum engine revs, the jet needle should
be raised.
If these faults should occur at the lower end of the part throttle range at a four-stroke running, make the idling range leaner; if the
engine pings, adjust the idling range richer.
Full throttle range D
Operation with the throttle fully open (flat out). This range is influenced by the main jet and the jet needle. If the porcelain of the
new spark plug is found to have a very bright or white coating or if the engine rings, after a short distance of riding flat out, a larger
main jet is required. If the porcelain is dark brown or black with soot the main jet must be replaced by a smaller one.
mixture too rich:
too much fuel in proportion to air
mixture too lean:
not enough fuel in proportion to air
1
2
OPERATING RANGES OF THE CARBURETOR

2-3C
Carburetor adjustment
Basic information on the original carburetor setting
The original carburetor setting was adapted for an altitude of approx. 500 meters (1600 ft.) above sea level, and the ambient
temperature of approx. 20° C (68° F), mainly for off-road use and central European premium-grade fuel (ROZ 95 MOZ). Mixing
ratio 2-stroke motor oil : super fuel 1:40 – 1:60.
Basic information on a change of the carburetor setting
Always start out from the original carburetor setting. Essential requirements are a clean air filter system, air-tight exhaust system and
an intact carburetor. Experience has shown that adjusting the main jet, the idling jet and the jet needle is sufficient and that changes
of other parts of the carburetor will not greatly affect engine performance.
RULE OF THUMB:
high altitude or high temperatures ➞choose leaner carburetor adjustment
low altitude or low temperatures ➞choose richer carburetor adjustment

WARNING

–O
NLY USE PREMIUM-GRADE GASOLINE ROZ 95 MIXED WITH HIGH-GRADE TWO-STROKE ENGINE OIL. OTHER TYPES OF GASOLINE CAN CAUSE ENGINE
FAILURE, AND USE OF SAME WILL VOID YOUR WARRANTY.
–O
NLY USE HIGH-GRADE 2-STROKE ENGINE OIL OF KNOWN BRANDS.
–N
OT ENOUGH OIL OR LOW-GRADE OIL CAN CAUSE EROSION OF THE PISTON. USING TOO MUCH OIL, THE ENGINE CAN START SMOKING AND FOUL THE
SPARK PLUG.
–I
NTHE CASE OF A LEANER ADJUSTMENT OF THE CARBURETOR PROCEED CAUTIOUSLY
. ALWAYS REDUCE THE JET SIZE IN STEPS OF ONE NUMBER TO AVOID
OVERHEATING AND PISTON SEIZURE.
NOTE: If despite a changed adjustment the engine does not run properly, look for mechanical faults and check the ignition system.
Basic information on carburetor wear
As a result of engine vibrations, throttle valve, jet needle, and needle jet are subjected to increased wear. This wear may cause
carburetor malfunction (e.g., overly rich mixture). Therefore, these parts should be replaced after 10000 kilometers (6000 miles).
Explanation - Example
Compared to the needle N 85 A, the jet needle N 85 C is two steps leaner
in the range from the closed position of the throttle to 1/4 throttle.
Otherwise, there are not differences.
!
CAUTION
!
WHEN CHANGING THE JET NEEDLE, MAKE SURE THAT YOU USE THE CORRECT NEEDLE
TYPE (N 85 ,NOZ OR N3). THE TECHNICAL DATASHEET TELLS YOU WHICH JET
NEEDLE CAN BE USED FOR WHICH MODEL.
N 85 C 0–1/4––
jet needle throttle valve open effect
N 85 A
N 85 B 0–1/4–
N 85 C 0–1/4––
N 85 D 0–1/4– – –
N 85 E 0–1/4– – – –
NOZ C
NOZ D 0–1/4–
NOZ E 0–1/4– –
NOZ F 0–1/4– – –
NOZ G 0–1/4– – – –
NOZ H 0–1/4– – – – –
NOZ I 0–1/4– – – – – –
NOZ J 0–1/4– – – – – – –
N3CG
N3CH 0–1/4–
N3CW 0–1/4– –

Repair manual KTM 250 / 300 / 380 Art No 3206004 -E
2-4C
Checking the setting of the TVC system
The function of the TVC system is checked with the engine running.
This test checks the start of advance and the end of advance.
–For this, remove the left control cover.
–Connect a rev counter (either to the ignition cable or to the blue/white
cable in the electronics box, depending on the rev counter design).
–Start engine, accelerate gently and observe when the TVC system
starts to advance (tooth segment creeps upwards).
–If necessary, turn the adjusting screw 1.
NOTE: Twisting the adjusting screw in delays the commencement of
adjustment by the TVC system, twisting the adjusting screw out means
that the TVC system will perform the adjustment earlier.
Bleeding of the hydraulic clutch
–Take off cover together with rubber bellows.
–At the slave cylinder of the clutch, remove the bleeder nipple 2. It its
place, mount the bleeder syringe 3which is filled with SAE 10
hydraulic oil.
–Refill oil, until oil is discharged from the bore 4of the master cylinder
in a bubble-free state. Make sure that the oil does not overflow.
!
CAUTION
!
–HAVING COMPLETED THE BLEEDING PROCEDURE, YOU HAVE TO VERIFY THAT THE
OIL LEVEL IN THE MASTER CYLINDER IS CORRECT.
–KTM USES BIODEGRADABLE HYDRAULIC OIL FOR THE HYDRAULIC CLUTCH
CONTROL. NEVER MIX BIODEGRADABLE HYDRAULIC OILS WITH MINERAL OILS.
–ALWAYS USE BIODEGRADABLE HYDRAULIC OIL SAE 10 TO FILL UP THE MASTER
CYLINDER. NEVER REFILL WITH MINERAL HYDRAULIC OIL OR BRAKE FLUID.
1
start of advance end of advance
250 Model 1999 5400 U/min 7550 U/min
250 from Modell 2000 on 5000 U/min 7000 U/min
300 up to Modell 2000 5300 U/min 7750 U/min
300 from Modell 2001 on 5900 U/min 7750 U/min
380 5200 U/min 7200 U/min
2
3
4

2-5C
Fig. Part no. Description
1560.12.001.000 Universal engine work stand
3546.29.003.000 Clutch holder
4560.12.004.000 Gear wheel segment
5546.29.009.044 Magneto extractor M 27x1 Kokusan
66276 807 Magneto extractor M 26x1,5 SEM
7510.12.011.000 Circlip plier
8544.12.012.000 Holding spanner for flywheel SEM
9584.29.037.040 Mounting tool inner ring NJ 207
9584.29.037.043 Mounting tool inner ring NJ 207
10 510.12.016.000 Protection cap
11 546.29.012.100 Holding spanner for flywheel Kokusan
13 501.12.013.000 Dial gauge 0-10 mm
14 501.12.030.000 Dial gauge support
16 6 899 785 Loctite 243 blue 6 ccm
17 151.12.017.000 Bearing puller
18 151.12.018.100 Internal bearing puller 18-23 mm
18 151.12.018.000 Internal bearing puller 12-16 mm
18 151.12.018.200 Internal bearing puller 5-7 mm
19 546.29.027.000 Clutch rivetting tool
25 0276 179 000 Extractor primary gear
26 503.29.050.000 Vent springe for hydraulic clutch
13
14
16
7
17
18
6
5
10
4
25
3
19
1
26
8
11
9
SPECIAL TOOLS – ENGINE 250 / 300 / 380

Repair manual KTM 250 / 300 / 380 Art No 3206004 -E
2-6C
Should you wish to make a pause over a longer space of time, please observe the following instructions:
–Clean motorcycle thoroughly (see chapter: CLEANING)
–Change engine oil (old engine oil contains aggressive contaminants).
–Check antifreeze and amount of cooling liquid.
–Let the engine warm up again, close fuel cock and wait until the engine dies off by itself. In this way the carburetor jets are prevented
from becoming resin- clogged by the old fuel.
–Remove spark plug and fill in approx. 5 ccm of engine oil into the cylinder through the opening. Actuate kick-starter 10 times in order
to distribute the oil onto the cylinder walls and mount the spark plug.
–Let fuel flow out of tank into an appropriate container.
–Correct tire pressure.
–Lubricate bearing points of the control levers, footrests, etc. as well as the chain.
–The storage place should be dry and not be subjected to too big temperature fluctuations.
–Cover the motorcycle with an air permeated tarp or blanket. Do not use non airtight materials as a possible humidity might not be
able to escape and thereby cause corrosion.
!
CAUTION
!
ITWOULD BE VERY BAD TO LET THE ENGINE RUN FOR A SHORT TIME DURING THE STORAGE PERIOD. THE ENGINE WOULD NOT GET WARMED UP ENOUGH AND
THE THUS DEVELOPED STEAM WOULD CONDENSE DURING THE COMBUSTION PROCESS AND CAUSE THE VALVES AND EXHAUST TO RUST.
USE AFTER A PERIOD OF STORAGE
–Fill up the tank with fresh fuel.
–Check the motorcycle as before each start (see driving instructions)
–Take a short, careful test ride first.
NOTE: Before you put your motorcycle away for the winter, you should check all parts for their function and wear. Should any service
jobs, repairs, or any refitting be necessary, you should have them carried out during the off-season (lower workload at mechanics'
shops). This way, you can avoid the long waiting times at your shop at the beginning of the next biking season.
STORAGE
Clean your motorcycle regularly in order to maintain the beauty of its plastic surfaces.
The best manner would be to use warm water that has been mixed with a normal brand-name washing detergent and a sponge.
The hard dirt can be removed before washing with the help of a soft water jet.
!
CAUTION
!
NEVER CLEAN YOUR MOTORCYCLE WITH A HIGH-PRESSURED CLEANER OR A HIGH-PRESSURED WATER JET. THE WATER COULD OTHERWISE RUN INTO THE
ELECTRICAL COMPONENTS, CONNECTORS, SHEATHED CABLES, BEARINGS, CARBURETOR, ETC. AND CAUSE DISTURBANCES OR LEAD TO A PREMATURE
DESTRUCTION OF THESE PARTS.
–Before cleaning with water, plug the exhaust pipe to prevent water ingress.
–You should use normal brand-name detergents to clean the motorcycle. Especially dirty parts should also be cleaned with the help
of a paint brush.
–After the motorcycle has been rinsed with a soft water jet, it should be dried by air pressure and a cloth. Then take a short drive until
the engine has reached the working temperature and also use the brakes. By warming these components, the residual water can
evaporate from inaccessable parts of the engine and the brakes.
–Slide back the protective covers on the handlebar-mounted instruments so that any water that may have seeped into this part of the
motorcycle is allowed to evaporate.
–After the motorcycle has cooled down, oil and grease all the gliding bearing parts. Treat the chain with a chain spray.
–To prevent failures in the electric system, you should treat the ignition lock, the emergency OFF switch, the short circuit button, the
light switch and the socket connectors with contact spray.
CLEANING
In the event that the motorcycle is also used in winter and on roads where one has to expect salt spraying, you will have to take
precautions against the aggressive road salt.
–clean the motorcycle thoroughly and let it dry after each ride
–treat the engine, carburetor, swing arm, and all other bare or galvanized parts (except for brake discs) with a wax-based anti-corro-
sion agent.

WARNING

K EEP THE ANTI - CORROSION AGENT FROM GETTING INTO CONTACT WITH THE BRAKE DISCS , OTHERWISE THIS WILL SIGNIFICANTLY REDUCE THE BRAKING POWER .
!
CAUTION
!
AFTER RIDES ON SALTED ROADS, CLEAN MOTORCYCLE THOROUGHLY WITH COLD WATER AND LET IT DRY WELL.
CONSERVATION FOR WINTER OPERATION