GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual
6 © 2010 American Honda Motor Co., Inc — All Rights Reserved
Maximum Operating Temperatures
These temperatures are based on an ambient temperature of 40°C (104°F). Compensate for any deviation linearly; i.e.,
if the ambient temperature is 20°C (68°F), the maximum acceptable oil temperature is 120°C (248°F).
Adjusted oil temperatures of less than 40°C will require more frequent oil changes.
Engine Enclosures
When the engine installation in the equipment obscures the emission label, a duplicate label must be applied. In this
case, as part of the engine matching process, it will be necessary to establish a process for the OEM to obtain
duplicate labels. EPA requires full documentation, control, and record keeping of the duplicate label process.
Cool Air Intake
The engine must be provided with a cooling duct so that fresh air can be drawn directly from outside the enclosure
cover. Install the cooling air duct with the intake port in a place free from dust and dirt. The cooling air volume changes
according to the shape of the duct and screen and the engine installation conditions. Operate the engine under the
normal operating conditions and be sure that the engine meets all temperature requirements.
The cooling air duct must have a cross-sectional area of at least 300 cm
2
(46.5 sq in).
When the engine is operated in dusty areas, install a filter at the enclosure inlet for the cooling air. This will reduce the
effective area, so you must increase the size of the inlet accordingly. Increase the size of the inlet to the point where
the maximum operating temperatures are not exceeded when operated under maximum load.
Install the cooling air duct and filter so that the filter can be easily checked, and dust, dirt and foreign material removed.
Hot Air Discharge
Hot air must be discharged directly outside the enclosure. Provide a discharge duct if necessary. The minimum cross
section of the hot air discharge opening must be larger than that of the cooling air inlet.
Locate the discharge port so the hot discharge air does not flow back into the enclosure. Provide sufficient ventilation to
prevent the engine compartment temperature from rising above ambient temperature limits after the engine has been
stopped.
Exhaust Discharge
The exhaust system becomes hot during operation and remains hot for a while after operation. Separate the exhaust
system from the engine compartment with a partition wall and locate the exhaust system in the discharged cooling air
flow.
Be sure the exhaust gas is directly discharged outside the enclosure without being blocked or restricted by any
obstacles. The exhaust gas must not flow back or be drawn back into the enclosure.
Provide the engine with an exhaust deflector or exhaust pipe extension if necessary.
If an extension pipe is used:
• Keep the length of the pipe as short as possible to keep exhaust backpressure within limits (see page 10).
• The extension pipe must have an ID larger than the OD of the muffler outlet.
• Verify the exhaust pipe extension does not create excessive vibration at any given engine rpm. If necessary, use
an exhaust pipe holder to support the exhaust pipe extension.
Grass Cutting Applications
When the engine is operated on grass cutting equipment, install a rotary screen grid on the cooling air intake port to
prevent the accumulation of large clippings.
Do not allow the grass clippings shredded by the rotary screen grid to accumulate around the intake port.
Spark plug Seat 270 °C (482 °F)
Engine Oil 140 °C (284 °F)
Gasoline at Carburetor Float Bowl 60 °C (140 °F)
Gasoline at Carburetor Float Bowl (after 5 min. hot soak) <70 °C (158 °F)
Gasoline at Fuel Tank 60 °C (140 °F)
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