FUEL SYSTEM
CS-2511TES
251Ts, 251TCs
35
4-8 Adjusting carburetor
4-8-1 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 filter element must be clean and properly installed.
3. The muffler exhaust port must be clear of carbon.
4. The fuel lines, tank vent and fuel filter are in good condition and clear of debris.
5. The fuel is fresh ( > 89 octa
ne : RON ) and
properly mixed at 50 : 1 with “ISO L-EGD” or “JASO FC/
FD” 2-stroke oil.
6. 20, 25 or 30 cm bar and chain must be installed, and properly tensioned.
B. Preliminary adjustment : Adjustment by Throttle adjust screw of carburetor.
Start and run engine for 100 seconds alternating engine speed between WOT 5 seconds and idle 5 sec-
onds. Verify idle engine speed ranges from 2,800 to 3,600 r/min, and WOT engine speed ranges 12,700
to 13,400 r/min. If idle engine speed is out of range, adjust throttle adjust screw to 2,800 - 3,600 r/min.
Make sure WOT engine speed in range 12,700 - 13,400 r/min again. If engine does not run correctly after
this adjustment, proceed to the next step 4-8-2.
4-8-2 Initial setting Throttle adjust screw, L mixture needle and H mixture needle
Tools Required : P/N G310-000050 Tachometer
PET-304, P/N X089-000094 Carburetor adjustment
tool KIT (D-shaped tool (L) and Driver(2.5mm))
1. Turn L and H mixture needles clockwise until
lightly seated, and then turn out both mixture nee-
dles following turns.
L mixture needle (B) : 1 7/8
H mixture needle (C) : 2 5/8
NOTE :
If needles are overtightened during seat-
ing, damage to carburetor may occur.
2. Remove air cleaner cover and air filter to see
the throttle adjust screw (D) contacts the throttle
plate (E) (Fig.1). Turn the screw(D) counterclock-
wise until its tip no longer touches the throttle plate
(E) (Fig.2). Then turn the screw (D) clockwise untill
its tip just comes into contact with the plate (E)
again (Fig.3). Finally, turn the screw (D) 1 5/8 turns
clockwise. Reinstall air filter and air cleaner cover.
NOTE :
The initial carburetor settings for throttle
adjust screw, L and H mixture needles are
intended to start and run the engine before final
carburetor adjustments are made to conform the
unit to meet Emission Directive. The actual number
of turns needed for engine operation may vary.
1
7
4
3 2
Fig.1
Fig.2
Fig.3
D
E
D
E
D
E
D
C
B
A
