Fuel - Stihl SR 420 Instruction Manual

English
4.3 Loosening the Harness
► Lift the tabs of the sliding adjusters.
► Adjust the harness so that the backplate fits
snugly and securely against your back.
4.4 Throwing Off Machine
Before using the machine, make yourself familiar
with how to release and throw off the backpack.
In an emergency, quickly throw the machine off
your back as follows:
► Open the quick-release fastener on the waist
belt (special accessory).
► Open the strap hook on the backplate by
snapping it forwards (arrow).
► Throw the machine to the rear.
5

Fuel

The engine requires a mixture of gasoline and
engine oil.
WARNING
Avoid direct skin contact with fuel and breathing
in of gasoline fumes.
5.1 STIHL MotoMix
STIHL recommends using STIHL MotoMix. This
pre-blended fuel is free of benzene and lead, is
distinguished by a high octane rating, and
always provides the proper mixing ratio.
10
STIHL MotoMix uses STIHL HP Ultra two-stroke
engine oil for optimum engine life.
MotoMix is not available in all markets.
5.2 Mixing fuel
NOTICE
Unsuitable fuels or a mixing ratio that deviates
from the specification can lead to severe engine
damage. The engine, seals, fuel lines and fuel
tank may be damaged if low-quality gasoline or
engine oil is used.
5.2.1 Gasoline
Use only high-quality gasoline with an octane rat‐
ing of at least 90 ROC – leaded or unleaded.
Gasoline with an alcohol component exceeding
10% can cause impaired engine performance in
engines with manually adjustable carburetors
and thus should not be used in these engines.
Engines with M-Tronic deliver full engine per‐
formance using gasoline with an alcohol compo‐
nent of up to 27% (E27).
5.2.2 Engine oil
If you mix the fuel yourself, use only STIHL two-
stroke engine oil or another high-performance
engine oil classified as JASO FB, JASO FC,
JASO FD, ISO-L-EGB, ISO-L-EGC or ISO-L-
EGD.
STIHL specifies STIHL HP Ultra two-stroke
engine oil or an equivalent high-performance
engine oil in order to maintain emission limits
over the machine's service life.
5.2.3 Mixing ratio
with STIHL two-stroke engine oil 1:50; 1:50 =
1 part oil + 50 parts gasoline
5.2.4 Examples
Quantity of gaso‐ STIHL two-stroke
line engine oil 1:50
Liters Liters
1 0.02
5 0.10
10 0.20
15 0.30
20 0.40
25 0.50
► Pour oil into an approved safety fuel canister
first, then add gasoline and mix thoroughly
5 Fuel
(ml)
(20)
(100)
(200)
(300)
(400)
(500)
0458-372-0121-C