SERVICE INFORMATION
SRM-420ES
7
2 CARBURETTOR ADJUSTMENT PROCEDURE
2-1 General adjusting rules
A. Before starting the unit for adjustment, check the following items.
1. The correct spark plug must be clean and properly gapped.
2. The air
fi
lter element must be clean and properly installed.
3. The muf
fl
er exhaust port must be clear of carbon.
4. The fuel lines, tank vent and fuel
fi
lter are in good condition and clear of debris.
5. The fuel is fresh ( > 89 octane : RON ) and properly mixed at 50 : 1 with “ISO L-EGD” or “JASO FC/FD” 2-stroke oil.
6. Install nylon line cutter with 2 nylon lines with 150 mm, even if 3-tooth blade is installed, for proper en-
gine loading to make sure engine speed on both SRM-420ES(L) and SRM-420ES(U).
B. Preliminary adjustment. Adjustment by Idle adjust screw of carburetor.
Start and run engine for 3 minute alternating engine speed between WOT for 50 seconds and idle for 10 sec-
onds. Adjust idle engine speed to 2,800 +/- 100 r/min by turning Idle adjust screw. Con
fi
rm WOT engine speed
approx. 10,000 r/min. If engine does not run correctly after this adjustment, proceed to the next step 2-2.
2-2 Presetting Idle adjust screw, L mixture needle and H mixture needle
Tools Required : Small screwdriver with 2.5 mm
blade, P/N G310-000050 electronic tachometer,
P/N Y089-000091 D-shaped tool (A).
1. Turn L and H mixture needle clockwise until
lightly seated, and then turn out both mixture nee-
dles following turns.
L mixture needle (B) : 2 3/8
H mixture needle (C) : 3
NOTE :
If needles are overtighented during seat-
ing, damage to carburettor may occur.
2. Remove air cleaner lid to expose the Idle adjust
screw and throttle plate. Turn Idle adjust screw (D)
anticlockwise until Idle adjust screw tip just touch-
es throttle plate. Then turn it clockwise 2 1/8 turns.
Reinstall air cleaner lid.
NOTE :
The initial carburettor settings for Idle ad-
just screw, Idle and H mixture needles are intended
to start and run the engine before
fi
nal carburettor
adjustments are made through this procedure. The
actual number of turns needed for engine opera-
tion may vary.
(A)
(D)
(C)
(B)
