EMISSIONS SERVICE BULLETIN
Ref No. 12-01R
Issued in: Jan. 2012
To: All RedMax Distributors and Dealers
Subject: Emission Carburetor: Low Speed Mixture Needle
and Altitude Adjustment Procedures (Fixed Main Jet)
Emissions Carburetor: Walbro-Model: WYL- 221 PART # 521600901 (848E488100)
From:
All units listed with above carburetor model
The carburetors on the listed model have been factory preset to C.A.R.B. Tier III and E.P.A Phase II
emissions regulations. The Idle-speed adjustment is controlled by idle speed throttle valve screw.
The Low-speed mixture needles has been preset and sealed to insure compliance with emission
regulations. The Low-speed Fuel mixture needle adjustment controls the Fuel/ Air mixture at idle and
mid-range engine speeds. The wide open throttle (WOT) speed operation is controlled by Fixed Main Jet.
Extended operation above 4000 ft, or after carburetor rebuild, requires readjustment of idle screw and
mixture needle to insure the engine continues to comply with C.A.R.B, and E.P.A, emission regulations.
1. REQUIRED TOOLS
Carburetor adjustment screw driver 2.5 mm flat tip, Limiter cap removal tool, Electronic digital
tachometer with sensitivity capable to within 10 RPM increments, and One (1) Limiter cap.
WARNING!!! DANGER!!!
Always operate unit in a well ventilated and clear work area. Keep hands clear of moving,
rotating, cutting attachment, or components during adjustment otherwise serious bodily injury
may occur.
2. PRE - ADJUSTMENT CHECK LIST
IMPORTANT: Before performing carburetor adjustment, the following areas must be inspected
and in good working order.
● Correct spark plug set to specified gap must be used.
Spark Plug: NGK-BPMR7Y Gap: 0.026 inch (0.65 mm)
● Standard nylon head must be installed with 7 inches (180 mm)
of line exposed on both sides.
● The air filter must be clean and properly installed.
● The carburetor and carburetor insulator block screws must be tight.
● The fuel filter must be clean and properly installed.
● The muffler spark arrestor screen and exhaust port must be clear
of carbon.
● The fuel must be fresh (≥ 89 Octane or higher: RON+MON/ 2) and
properly mixed at 50:1 ratio with RedMax or (ISO-L-EGD/ JASO
FD) registered 2-stroke oil.
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