NOTICE
Remove the tool used to block the shaft.
Removing the Cutting Attachment
Block the shaft.
N
Unscrew the mounting nut
N
clockwise.
Pull the cutting attachment with its
N
mounting hardware off the
gearhead.
FS 310
Fuel
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.
For further details, see
www.STIHLusa.com/ethanol
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
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