Carburetor Adjustment; Lpg-Only Operation - Vanguard OHV V-Twin User Manual

GASEOUS FUEL CARBURETOR
ADJUSTMENT
Some Briggs & Stratton V-Twin engines were
available factory-built to operate on liquefied
petroleum gas (LPG) or natural gas (NG). To
maintain the California Air Resource Board (CARB)
emissions certification on these engines, the
Original Equipment Manufacturer (OEM) must use
specific equipment and procedures to complete the
installation. The following describes the OEM
requirements. Always have a certified LPG/NG
technician perform repairs on gaseous fuel systems.
NOTE: The main adjustment is the large brass
adjustment screw (1) just to the left of the
solenoid (2) and capped port (3), Fig. 58.
The idle adjustment is located below and to
the left of the main adjustment. An accurate
CO meter is required to adjust the gaseous
fuel mixture.
1. Start the engine. Set the main mixture adjust-
ment at high speed under load to achieve 1/2 –
1% CO in the exhaust.
2. Allow the engine to warm up at top speed for 2
minutes.
3. Slow the engine to between 1100 – 1750 no-load
RPM. Adjust the idle mixture to achieve 1/2 – 1%
CO in the exhaust.
4. Return the engine to high speed full-load. If
required, readjust the setting to 1/2 – 1% CO.
5. Stop the engine. Install the anti-tampering
plugs.
Fig. 58

LPG-Only Operation

NOTE: If the application is designed so that the
engine normally operates on NG, but
defaults to LPG if the NG supply is
interrupted, no adjustments for LPG
operation are required. The following steps
describe the setting procedure when the
engine is ONLY powered by LPG.
1. Follow steps 1 through 4 above. The same
components (regulators, lock-off, fuel lines, etc.)
used with the NG installation are used for the
LPG installation.
2. Connect the fuel transfer solenoid to a 12 volt
DC power supply. As an alternative the main
adjustment screw may be turned in until
completely seated eliminating the need for
applying power to the solenoid.
3. Start the engine and run it at top speed for 2
minutes to warm up. The engine uses a fixed
main jet for LPG operation, no adjustment is
necessary.
4. Slow the engine to 1100 – 1750 RPM no-load.
Adjust the idle mixture to achieve a reading of up
to 3% CO.
5. Stop the engine. Install the anti-tampering
plugs.
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