Benchmark BG4500i, Manual

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18
Carburetor Modification for High Altitude Operation (Above 2,000 feet)
NOTE
This engine is equipped to run at altitudes below 2,000-ft.
A high-altitude Main Jet is recommended when operated at 2,000 to
7,000-ft above sea level.
At elevations above 7,000-ft the engine may experience decreased
performance even with a high-altitude Main Jet.
At high altitudes the carburetor’s air/fuel mixture becomes too rich, resulting in
higher fuel consumption, lower performance, and carbon build-up on the spark plug.
On the other hand, if the carburetor has been modified for high altitude operation
and is operated below 2000-ft, the air/fuel mixture will then be too lean for low
altitude use. Always use the correct Main Jet for your altitude.
The engine’s carburetor, governor (if so equipped), and any other parts that control
the air/fuel ratio will need to be adjusted by a qualified mechanic to allow efficient
high-altitude use, and to prevent damage to the engine and any other devices used
with this product. The fuel system on this engine may be influenced by operation at
higher altitudes.
Carburetor bowl may have gas in it which will leak upon removing the
bolt.
The mixing tube is held in place by the Main Jet and might fall out when
it is removed. If it falls out, replace it in the same orientation before
replacing the Main Jet.
The Fuel Cup Seal and Bolt Seal may be damaged during removal and
should be replaced with the new ones.
Carburetor
Assembly
Main Jet
Fuel Cup Seal
Mixing Tube
(might remain
inside carburetor)
Fuel Cup
Bolt Seal
Bolt
Drain Bolt
Washer