Adjusting Carburetor - Echo PB-251 Service Manual

PB-251

5-5 Adjusting carburetor

GENERAL ADJUSTMENT RULES:
Before starting the unit for adjustment, check the following items.
a. Correct spark plug must be clean and properly gapped.
b. Air filter must be clean and properly installed.
c. Muffler exhaust port must be clear of carbon.
d. Fuel lines, tank vent and fuel strainer are in good condition and clear of debris.
e. Fuel is fresh ( > 89 octane :
FC/FD" 2 stroke oil.
f. All blower pipes are installed for proper engine loading.
Start and run engine for 3 minutes alternating rpm between WOT for 50 seconds and idle for 10 seconds.
Adjust idle adjust screw to 3,000 +/- 200 rpm. If engine does not run correctly after this adjustment, proceed
to the next steps.
IMPORTANT: After adjusting carburetor according to the next steps, the limiter plugs must be
installed in idle and hi speed (H) mixture needles to comply with Emission regulation.
(D)
(C)
FUEL SYSTEM
RON+MON
) and properly mixed at 50 : 1 with "ISO L-EGD" or "JASO M345-
2
(A)
(B)
(1)
(2)
(D)
(3)
(G)
(D)
Fig1
REQUIRED TOOLS & PARTS: Small screwdriver
with 2.5 mm blade, P/N 990511-30017 electronic
tachometer, P/N 91020 limiter plug tool, P/N P005-
001270 limiter plugs.
1. Remove limiter plugs from idle mixture needle
hole (A) and H mixture needle hole (B) using limiter
plug tool (C) as follows.
(1)Put limiter plug tool (C) on limiter plug in mixture
needle hole.
(2)Screw limiter plug tool counterclockwise 2 turns
into limiter plug pushing the tool against the plug to
engage tool threads.
(3)Pull out limiter plug tool with the limiter plug from
mixture needle hole.
(A)
(4)Repeat plug removal procedure for the other mix-
ture needle.
NOTE: If the plug is damaged and left in the hole,
use a needle or pin-shaped tool to remove deformed
plug pieces.
(G)
2. Turn H mixture needle (B) clockwise until lightly
seated. And then turn H mixture needle counter-
clockwise 1 1/8 turns. Turn idle mixture needle (A)
clockwise until lightly seated. And then turn idle mix-
ture needle counterclockwise 5 3/8 turns.
3. Turn idle adjust screw (D) clockwise until its head
touches boss (G) as shown Fig 1. Then turn idle
adjust screw (D) counterclockwise 5 turns.
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