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4-110 2002 Buell S3T: Fuel System
EVAPORATIVE EMISSIONS CONTROL 4.42
GENERAL
Buell motorcycles sold in the state of California are equipped
with an evaporative (EVAP) emissions control system. The
EVAP system prevents fuel hydrocarbon vapors from escap-
ing into the atmosphere and is designed to meet the Califor-
nia Air Resource Board (CARB) regulations in effect at the
time of manufacture.
The EVAP functions in the following manner:
● See Figure 4-109. Hydrocarbon vapors in the fuel tank
are directed through the vent valve and stored in the car-
bon canister. If the vehicle is tipped at an abnormal
angle, the vent valve closes to prevent liquid gasoline
from leaking out of the fuel tank through the fuel tank
vent hose.
● See Figure 4-110. When the engine is running, manifold
venturi negative pressure (vacuum) slowly draws off the
hydrocarbon vapors from the carbon canister through the
canister vent hose. These vapors pass through the throt-
tle body and are burned as part of normal combustion in
the engine. The large diameter canister-to-air cleaner
backplate hose (canister fresh air inlet hose) supplies the
canister with fresh air from the air cleaner.
TROUBLESHOOTING
11WARNING1WARNING
Verify that the evaporative emissions system hoses do
not contact hot exhaust or engine parts. The hoses con-
tain flammable vapors that can be ignited if damaged,
which could result in death or serious injury.
The system has been designed to operate with a minimum of
maintenance. Check that all hoses are properly routed and
connected and are not pinched or kinked. Periodically check
all mounting hardware for tightness.
Figure 4-109. Vent Valve Operation
Figure 4-110. Carbon Canister Installed
VEHICLE UPRIGHT
Check ball holds post to
side allowing hydrocar-
bon vapors to be
released to canister
through top of vent valve
VEHICLE TIPPED
Spring forces post to
seal against opening
preventing liquid gaso-
line from escaping fuel
tank
b0741a4x
Gasoline
Post
Check Ball
Vent Valve
8295
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