This manual covers engine selection, engine installation design and engine installation testing, so the combination of a Honda engine and your equipment will make the best possible product. Please feel free to contact your Honda Engine Distributor at any time for additional technical information or to discuss your engine application needs.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual NTRODUCTION Honda engines are designed for minimal maintenance. When maintenance is required, the task is kept simple by providing convenient maintenance access and procedures. Honda engines use proven engine technology and design innovations to make them highly reliable engines.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual ECOMMENDED OWER ANGE Maximum Operation Operate the engine at not more than 90% of the maximum horsepower available at a given rpm. Recommended maximum operating hp = 0.9 x maximum hp...
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GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual GX340 GX390 (N·m) (lbf·ft) (N·m) (kgf·m) (kgf·m) (lbf·ft) NET TORQUE NET TORQUE (KW) (HP) (KW) (HP) (PS) NET POWER NET POWER RECOMMENDED OPERATING SPEED RANGE RECOMMENDED OPERATING SPEED RANGE (min...
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Output Confirmation Methods Governor Rod Measurement When the engine is properly matched and operating at its continuous rated load, the carburetor throttle angle should be approximately half way between full open and full closed positions.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual YSTEM If the engine is supplied with an incomplete fuel system (no fuel tank, no fuel hose, etc.), the OEM is responsible for ensuring evaporative emission requirements/regulations are met, including certification.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Carburetor Controls Types of cable: Two types can be used, flexible wire core or solid wire. Installation: The throttle and choke control levers are provided with holes for optional cable attachment. The following illustrations show installation examples for a solid wire cable and for a flexible, braided wire cable.
Fabricated Exhaust Systems The muffler type and the shape and length of the exhaust pipe(s) affect emissions performance and engine power. If you use a muffler other than a recommended Honda muffler, observe the following precautions to maintain the engine’s peak performance: •...
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Rigid Engine Mount Muffler Installation. The frame must be rigid to prevent cracking when the exhaust pipe and muffler are connected. The muffler should be installed securely with bolts and nuts.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Engine Acceleration/Vibration Using a vibration meter, measure the vibration amplitude at the base on three axis (vertical, lateral and horizontal). Direction Allowable G value (Peak) (RMS) Vertical 10 (98 m/s 6.9 (68 m/s...
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Manual start Use a two-position engine switch with continuity between its terminals as shown. Wire Color EXT+ EXT – (Red) (Black) Switch Position Charging Coil Selection Four types of coils are available:...
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual OWER RANSMISSION V-Belt Connections Be sure there is no static axial load applied PULLEY CRANKSHAFT to the crankshaft. Axial Install the pulley as close to the base of the PTO shaft as possible. When installing...
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual To reduce resonance, install a stay between the engine and attachment as shown below. Starting Performance The engine must be able to start with the attachment at the lowest recommended ambient temperature.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual NSTALLATION ONSIDERATIONS Maintenance Points Accessibility When the engine is installed in an enclosure, provide an access panel or use an engine enclosure that can be opened and closed easily. See also Serviceability page 40.
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GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Right Side Fuel cap FUEL FILLER CAP Oil filler/cap dipstick Engine oil drain plug FUEL TANK Electric starter Electrical connections ELECTRICAL ELECTRIC STARTER CONNECTIONS (applicable types) OIL FILLER CAP/DIPSTICK OIL DRAIN PLUG...
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual IMENSIONS AND EIGHTS GX240 P.T.O. VARIATION Model P.T.O. GX240R2 GX240RT2 GX240U2 GX240UT2 Overall E type 360 mm (14.2 in) length H type 425 mm (16.7 in) L type 405 mm (15.9 in) 405 mm (15.9 in)
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GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual EQUIPMENT VARIATION Indicates the difference compared with values of P. T. O. variation above. Variation No balancer type Cyclone air cleaner Starter motor type Control box type Low profile type *1...
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual GX270 P.T.O. VARIATION Model P.T.O. GX270UT2 Overall length E type 340 mm (13.4 in) H type 425 mm (16.7 in) P type 380 mm (15.0 in) Q type S type 355 mm (14.0 in)
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual GX340 P.T.O. VARIATION Model P.T.O. GX340R2 GX340RT2 GX340U2 GX340UT2 Overall E type 365 mm (14.4 in) length H type 452 mm (17.8 in) L type 440 mm (17.3 in) P type 405 mm (15.9 in)
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual GX390 P.T.O. VARIATION Model P.T.O. GX390RT2/R2 GX390T2 GX390UT2/T2 Overall length H type 452 mm (17.8 in) L type 440 mm (17.3 in) P type 405 mm (15.9 in) Q type 405 mm (15.9 in)
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual ERVICEABILITY The following Maintenance section is duplicated from the applicable shop manual and is accurate at the time of publication of this manual. Page number cross references refer to the shop manual it was copied from. It is provided for your reference in considering serviceability issues.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Engine Oil Level Check Place the engine on a level surface. Remove the oil filler cap (1), and wipe the oil level gauge (2) clean. Insert the oil filler cap without screwing it into the oil filler neck (3).
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Engine Oil Change Drain the oil in the engine while the engine is warm. Warm oil drains quickly and completely. Place the engine on a level surface, and place a suitable container under the drain plug bolt.
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GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Cyclone Type: A dirty air filter will restrict air flow to the carburetor, reducing engine performance. If the engine is operated in dusty areas, clean the air cleaner more often than specified in the MAINTENANCE SCHEDULE.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Inner Filter (paper) Type: Tap the inner filter (1) lightly several times on a hard surface to remove excess dirt, or blow compressed air lightly (207 kPa (2.11 kgf/cm , 30 psi) or less) through the paper filter from the inside out.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Spark Plug Check/Adjustment CAUTION If the engine has been running, the engine will be very hot. Allow it to cool before proceeding. Remove the spark plug cap, and then remove the spark plug (1) using a spark plug wrench (2).
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Spark Plug Replacement CAUTION If the engine has been running, the engine will be very hot. Allow it to cool before proceeding. Remove the spark plug cap, and then remove the spark plug (1) using a spark plug wrench (2).
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Separated Protector Type Remove the muffler cover, if equipped. Remove the 4 x 6 mm tapping screws (1), and exhaust deflector (2), if equipped. Remove the 5 x 8 mm tapping screws (3), R. muffler protector (4), and L.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Valve Clearance Check/Adjustment Remove the head cover bolt (1), the head cover (2), and the head cover packing (3). Disconnect the spark plug cap from the spark plug. Set the piston near top dead center of the cylinder compression stroke (both valves fully closed) by pulling the recoil starter slowly.
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GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Hold the rocker arm pivot (1) and loosen the pivot adjusting nut (2). Turn the rocker arm pivot to obtain the specified clearance. VALVE CLEARANCE: IN: 0.15 ± 0.02 mm EX: 0.20 ±...
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual Fuel Tank and Filter Cleaning WARNING Gasoline is highly flammable and explosive. You can be burned or seriously injured when handling fuel. • Keep heat, sparks, and flame away. • Handle fuel only outdoors.
GX240 • GX270 • GX340 • GX390 (UT2/RT2) Technical Manual VAPORATIVE EMISSIONS Types with OEM provided fuel tanks The OEM is responsible for meeting the EVAP emissions regulations for products sold in California (California Air Resources Board) and the 49 sates (U.S. Environmental Protection Agency). This regulations concern evaporative emissions from the fuel system.