Stihl Km 90 R Owners Manual

							KM 90 R
English
9
WARNING
Never test the ignition system with the 
ignition wire boot removed from the 
spark plug or with a removed spark plug, 
since uncontained sparking may cause 
a fire.
WARNING
Do not operate your power tool if the 
muffler is damaged, missing or modified. 
An improperly maintained muffler will 
increase the risk of fire and hearing loss. 
Your muffler is equipped with a spark-
arresting screen to reduce the risk of 
fire; never operate your power tool if the 
screen is missing, damaged or clogged. 
Remember that the risk of a brush or 
forest fire is greater in hot or dry 
weather.
In California, it is a violation of § 4442 or 
§ 4443 of the Public Resources Code to 
use or operate gasoline-powered tools 
on forest-covered, brush-covered or 
grass-covered land unless the engine’s 
exhaust system is equipped with a 
complying spark arrester that is 
maintained in effective working order. 
The owner/operator of this product is 
responsible for properly maintaining the 
spark arrester. Other states or 
governmental entities/agencies, such as 
the U.S. Forest Service, may have 
similar requirements. Contact your local 
fire agency or forest service for the laws 
or regulations relating to fire protection 
requirements.
Store the power tool in a dry and high or 
locked location out of reach of children.Before storing for longer than a few 
days, always empty the fuel tank. See 
chapter "Storing the machine" in this 
manual. 
						

							KM 90 R
English
10The following STIHL KombiTools may 
be mounted on the KombiEngine:
Approved KombiTools
HT-KMBF-KM
464BA025 KN
KW-KMKB-KM
FH-KMFSB-KMBG-KM
FBD-KM
FS-KMFS-KM
FCS-KMFCB-KM
.RPEL7RRO
WKHEDUULHUEDURQWKHORRSKDQGOH
VXSSOLHGZLWKWKHPDFKLQHPXVWEH
XVHG
						

							KM 90 R
English
11 A barrier bar is supplied with the 
machine. Attach the barrier bar to the 
loop handle.
NInsert square nuts (1) in the barrier 
bar (2) – the holes must line upNInsert the clamp(3) in the loop 
handle (4) and position them 
together on the shaft (5)
NPosition clamp (6)
NPosition barrier bar (2) – note 
position!
NLine up the holes
NInsert bolts (7) in the holes – and 
screw them into the barrier bar as 
far as possibleNFit the loop handle (4) at a distance 
of (A) approx. 20 cm (8 in) forward 
of the control handle (8)
NOrient the loop handle
NTighten the bolts – lock the nuts if 
necessary
The sleeve (9) is present depending on 
the country and must be located 
between the loop handle and control 
handle.
Always leave the barrier bar attached.
Mounting the Loop Handle
2
002BA098 KN
11
5 4
002BA099 KN
2
3
6
7
A
9
8
4
002BA353 KN 
						

							KM 90 R
English
12 A properly adjusted throttle cable is the 
precondition for correct operation in the 
starting throttle, idle and full throttle 
positions.
Adjust the throttle cable only when the 
machine is completely and properly 
assembled.
NUse a suitable tool to push the slide 
to the end of the slot (see 
illustration).
NPress down the trigger lockout (1) 
and squeeze the throttle trigger (2) 
(full throttle position) – this sets the 
throttle cable correctly.This engine is certified to operate on 
unleaded gasoline and the STIHL two-
stroke engine oil at a mix ratio of 50:1.
Your engine requires a mixture of high-
quality gasoline and two-stroke air 
cooled engine oil.
Use mid-grade unleaded gasoline with a 
minimum octane rating of 89 ((R+M)/2) 
and no more than 10% ethanol content.
Fuel with a lower octane rating may 
increase engine temperatures. This, in 
turn, increases the risk of piston seizure 
and damage to the engine.
The chemical composition of the fuel is 
also important. Some fuel additives not 
only detrimentally affect elastomers 
(carburetor diaphragms, oil seals, fuel 
lines, etc.), but magnesium castings and 
catalytic converters as well. This could 
cause running problems or even 
damage the engine. For this reason 
STIHL recommends that you use only 
high-quality unleaded gasoline!
Gasoline with an ethanol content of 
more than 10% can cause running 
problems and major damage in engines 
and should not be used.
The ethanol content in gasoline affects 
engine running speed – it may be 
necessary to readjust the carburetor if 
you use fuels with various ethanol 
contents.
WARNING
To reduce the risk of personal injury 
from loss of control and / or contact with 
the running cutting tool, do not use your unit with incorrect idle adjustment. At 
correct idle speed, the cutting tool 
should not move.
If your power tool shows an incorrect idle 
adjustment, have your STIHL dealer 
check your power tool and make proper 
adjustments and repairs.
The idle speed and maximum speed of 
the engine change if you switch from a 
fuel with a certain ethanol content to 
another fuel with a much higher or lower 
ethanol content.
This problem can be avoided by always 
using fuel with the same ethanol 
content.
Use STIHL HP Ultra oil or ask your 
dealer for an equivalent high quality oil 
to ensure the maximum performance of 
the product for the full lifetime.
To meet the requirements of EPA 
40CFR90/1054 we recommend to use 
STIHL HP Ultra oil.
Do not use BIA or TCW rated (two-
stroke water cooled) mix oils or other 
mix oils that state they are for use in both 
water cooled and air cooled engines 
(e.g., outboard motors, snowmobiles, 
chain saws, mopeds, etc.).
Take care when handling gasoline. 
Avoid direct contact with the skin and 
avoid inhaling fuel vapor. When filling at 
the pump, first remove the container 
from your vehicle and place the 
container on the ground before filling. To 
reduce the risk of sparks from static 
discharge and resulting fire and/or 
explosion, do not fill fuel containers that 
are sitting in or on a vehicle or trailer.
Adjusting the Throttle Cable
002BA163 KN
21002BA161 KN
)XHO 
						

							KM 90 R
English
13 The container should be kept tightly 
closed in order to limit the amount of 
moisture that gets into the mixture.
The machine’s fuel tank should be 
cleaned as necessary.
Fuel mix ages
Only mix sufficient fuel for a few days 
work, not to exceed 30 days of storage. 
Store in approved fuel-containers only. 
When mixing, pour oil into the container 
first, and then add gasoline. Close the 
container and shake it vigorously by 
hand to ensure proper mixing of the oil 
with the fuel.
Dispose of empty mixing-oil containers 
only at authorized disposal locations.
Preparations
NBefore fueling, clean the filler cap 
and the area around it to ensure that 
no dirt falls into the tank.
Always thoroughly shake the mixture in 
the canister before fueling your 
machine.
NPosition the machine so that the 
filler cap is facing up.
WARNING
In order to reduce the risk of fire and 
personal injury from escaping gas vapor 
and fumes, remove the fuel filler cap 
carefully so as to allow any pressure 
build-up in the tank to release slowly.
Opening the filler cap
NTurn the cap counterclockwise until 
it can be removed from the tank 
opening.
NRemove the filler cap.
Refueling
Take care not to spill fuel while fueling 
and do not overfill the tank.
Closing the filler cap
NPosition cap.
NTurn the cap clockwise as far as it 
will go and tighten it as securely as 
possible by hand. Gasoline Oil (STIHL 50:1 or equiva-
lent high-quality oils)
Liters Liters (ml)
10.02(20)
5 0.10 (100)
10 0.20 (200)
20 0.40 (400)
US gal. US fl.oz.
12.6
2 1/2 6.4
512.8
Fueling
266BA028 KN
2709BA003 KN
2709BA004 KN 
						

							KM 90 R
English
14
Controls
1Throttle trigger lockout
2Throttle trigger
3Slide control
Positions of slide control
4STOP-0– engine off – ignition is 
switched off
5F– normal run position – the engine 
is running or can start
6START – ignition is switched on – 
the engine can startSymbol on slide control
7h – stop symbol and arrow. To stop 
the engine, push the slide control in 
the direction of the arrow on the stop 
symbol (h) to STOP-0.
Starting
NPress down the trigger lockout lever 
and squeeze the throttle trigger
Nand hold them in that position.
NMove the slide control to START 
and hold it there.
NNow release the throttle trigger, 
slide control and trigger lockout in 
that order. This is the starting 
throttle position.
NSet the choke knob (8) toNPress the manual fuel pump 
bulb (9) at least five times – even if 
the bulb is filled with fuel.
Cranking
NPlace the power tool on the ground 
so that it rests on the machine 
support:
NIf fitted: Remove the transport guard 
from the cutting attachment.
To reduce the risk of accidents, check 
that the working tool is not touching the 
ground or any other obstacles – see also 
"Starting / Stopping the Engine" in the 
KombiTool instruction manual.
Starting / Stopping the 
Engine
3
STOP
2
5
6 4 7
002BA181 KN
START
STOP-
1
249BA057 KN
9
8
gif the engine is cold
efor warm start – also use this posi-
tion if the engine has been running 
but is still cold.
552BA014 KN
552BA015 KN 
						

							KM 90 R
English
15 NMake sure you have a firm footing, 
either standing, stooping or 
kneeling.
NHold the unit firmly on the ground 
with your left hand and press down 
– thumb under the fan housing – do 
not touch the throttle trigger or 
trigger lockout.
NOTICE
Do not stand or kneel on the drive tube.
NHold the starter grip with your right 
hand.
NPull the starter grip slowly until you 
feel it engage and then give it a brisk 
strong pull.
NOTICE
Do not pull out the starter rope all the 
way – it might otherwise break.
NDo not let the starter grip snap back. 
Guide it slowly back into the housing 
so that the starter rope can rewind 
properly.
NContinue cranking.
NAfter no more than five pulls, move 
the choke knob to e.
When engine begins to fire
NContinue cranking.As soon as the engine runs
NBlip the throttle trigger immediately. 
The slide control moves to the 
normal run positionF – and the 
engine settles down to idle speed.
WARNING
Make sure the carburetor is correctly 
adjusted. The working tool must not 
move when the engine is idling.
Your machine is now ready for 
operation.
Stopping the Engine
NPush the slide control in the 
direction of the arrow on the stop 
symbol (h) to STOP-0.
At very low outside temperatures
As soon as the engine runs:
NBlip the throttle trigger to disengage 
the starting throttle position. The 
slide control moves to the normal 
run positionF – and the engine 
settles down to idle speed.
NOpen the throttle slightly.
NWarm up the engine for a short 
period.
If the engine does not start
Choke knob
If you did not turn the choke knob to e 
quickly enough after the engine began to 
fire, the combustion chamber is flooded.NTurn the choke knob to e
NSet the slide control, lockout lever 
and throttle trigger to the starting 
throttle position.
NStart the engine by pulling the 
starter rope briskly – 10 to 20 pulls 
may be necessary.
If the engine still does not start
NMove the slide control to STOP-0.
NRemove the spark plug – see 
"Spark Plug".
NDry the spark plug.
NCrank the engine several times with 
the starter to clear the combustion 
chamber.
NRefit the spark plug – see "Spark 
Plug".
NMove the slide control to START.
NSet the choke knob to e – even if 
the engine is cold.
NNow start the engine.
Throttle cable adjustment
NCheck adjustment of throttle cable – 
see chapter on "Adjusting the 
Throttle Cable".
Fuel tank run until completely dry
NAfter refueling, press the manual 
fuel pump bulb at least five times – 
even if the bulb is filled with fuel.
NSet the choke knob according to 
engine temperature.
NNow start the engine.
552BA016 KN 
						

							KM 90 R
English
16
During break-in period
A factory-new machine should not be 
run at high revs (full throttle off load) for 
the first three tank fillings. This avoids 
unnecessary high loads during the 
break-in period. As all moving parts 
have to bed in during the break-in 
period, the frictional resistances in the 
engine are greater during this period. 
The engine develops its maximum 
power after about 5 to 15 tank fillings.
During Operation
After a long period of full throttle 
operation, allow the engine to run for a 
short while at idle speed so that engine 
heat can be dissipated by the flow of 
cooling air. This protects engine-
mounted components (ignition, 
carburetor) from thermal overload.
After Finishing Work
Storing for a short period: Wait for the 
engine to cool down. Empty the fuel tank 
and keep the machine in a dry place, 
well away from sources of ignition, until 
you need it again. For longer out-of-
service periods – see "Storing the 
Machine".If there is a noticeable loss of engine 
power
NTurn the choke knob to g
NTake out the screw (1) and remove 
the filter cover (2). 
NClean away loose dirt from around 
the filter.
NGrip the filter element (3) at the 
cutout (arrow) in the filter 
housing (4) and remove it.
NFit a new filter element. As a 
temporary measure you can knock it 
out on the palm of your hand or blow 
it out with compressed air. Do not 
wash.
NReplace damaged parts.
Installing the filter
NInstall the filter element in the filter 
housing and fit the cover.
NInsert the screw and tighten it down 
firmly.Exhaust emissions are controlled by the 
design of the fundamental engine 
parameters and components (e.g. 
carburation, ignition, timing and valve or 
port timing) without the addition of any 
major hardware.
Operating InstructionsCleaning the Air Filter
1
273BA006 KN
2
4
(QJLQH0DQDJHPHQW 
						

							KM 90 R
English
17 The carburetor has been set at the 
factory to provide an optimum fuel-air 
mixture under most operating 
conditions.
Adjusting Idle Speed
Engine stops while idling
NWarm up the engine for about 
3 minutes.
NTurn the idle speed screw (LA) 
slowly clockwise until the engine 
runs smoothly – the cutting 
attachment must not rotate.
Attachment runs when engine is idling
NTurn the idle speed screw (LA) 
slowly counterclockwise until the 
cutting attachment stops running 
and then turn the screw about 
another 1/2 to 3/4 turn in the same 
direction.
WARNING
If the attachment continues to run when 
the engine is idling, have your machine 
checked and repaired by your servicing 
dealer.The muffler is equipped with a spark 
arresting screen.
NIf the engine is down on power, 
check the spark arresting screen in 
the muffler.
NWait for the muffler to cool down.
NMove the slide control to STOP-0.
NTake out the screw (1).
NTake out the screws (2) and remove 
the shroud (3).NTake out the screw (4).
NLift the spark arresting screen (5) 
and pull it out.
NClean the spark arresting screen. If 
the screen is damaged or heavily 
carbonized, fit a new one.
NRefit the spark arresting screen.
NInsert screw and tighten it down 
firmly.
NInstall the shroud.
Adjusting the Carburetor
266BA027 KNLA
6SDUN$UUHVWLQJ6FUHHQLQ
0XIIOHU
249BA059 KN
1
2
3
2249BA060 KN 
						

							KM 90 R
English
18 If engine is down on power, difficult to 
start or runs poorly at idling speed, first 
check the spark plug.
Fit a new spark plug after approx. 100 
operating hours or earlier if the 
electrodes are badly eroded.
Wrong fuel mix (too much engine oil in 
the gasoline), a dirty air filter and 
unfavorable running conditions (mostly 
at part throttle etc.) affect the condition 
of the spark plug. These factors cause 
deposits to form on the insulator nose 
which may result in trouble in operation.
Removing the spark plug
NMove the slide control to STOP-0.
NPull off the spark plug boot (1).
NUnscrew the spark plug.
Checking the Spark Plug
NClean dirty spark plug.
NCheck electrode gap (A) and 
readjust if necessary – see chapter 
"Specifications."
NUse only resistor type spark plugs of 
the approved range.
Rectify problems which have caused 
fouling of spark plug:
–too much oil in fuel mix,
–dirty air filter,
–unfavorable running conditions, e.g. 
operating at part load.
WARNING
T o  r e d u c e  t h e  r i s k  o f  f i r e  a n d  b u r n  i n j u r y ,  
use only spark plugs authorized by 
STIHL. Always press spark plug boot (1) 
snugly onto spark plug terminal (2) of the 
proper size. (Note: If terminal has 
detachable SAE adapter nut, it must be 
securely attached.) A loose connection 
between spark plug boot and ignition 
wire connector in the boot may create 
arcing that could ignite combustible 
fumes and cause a fire.
Spark Plug
1
249BA063 KN
000BA039 KNA
2
1
002BA363 KN