Honda GX340 Engine Instruction Manual
Honda GX340 Engine
Honda GX340 Engine Instructions
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Honda GX340 Engine Specifications
| Feature | Specification |
|---|---|
| Engine Model | Honda GX340 (GX340UT1 / GX340RT1 types) |
| Engine Type | 4-stroke, overhead valve, single cylinder |
| Displacement | 337 cm³ (20.6 cu-in) |
| Bore × Stroke | 82.0 × 64.0 mm (3.2 × 2.5 in) |
| Net Power (SAE J1349) | 7.1 kW (9.7 PS, 9.5 bhp) at 3,600 rpm |
| Max. Net Torque (SAE J1349) | 22.1 N·m (2.25 kgf·m, 16.3 lbf·ft) at 2,500 rpm |
| Dimensions (L × W × H) | 380 × 450 × 447 mm (15.0 × 17.7 × 17.6 in), PTO shaft type S with fuel tank |
| Dry Mass | 31.5 kg (69.4 lbs) |
| Engine Oil Capacity | 1.1 L (1.2 US qt, 1.0 Imp qt) |
| Fuel Tank Capacity | 6.1 L (1.61 US gal, 1.34 Imp gal) |
| Cooling System | Forced air |
| Ignition System | Transistor magneto |
| PTO Shaft Rotation | Counterclockwise |
| Recommended Fuel | Unleaded gasoline, pump octane 86 or higher (research octane 91 or higher) |
| Maximum Alcohol Content in Fuel | 10% ethanol (E10) or 5% methanol by volume |
| Recommended Engine Oil | SAE 10W-30, API SJ or later (4-stroke automotive detergent oil) |
| Reduction Case Oil Capacity | 0.30 L (0.32 US qt, 0.26 Imp qt), applicable types |
| Oil-Bath Air Cleaner Oil Capacity | 80 cm³ (2.7 US oz, 2.8 Imp oz) |
| Recommended Spark Plugs | BPR6ES (NGK), W20EPR-U (DENSO) |
| Spark Plug Gap | 0.7–0.8 mm (0.028–0.031 in) |
| Spark Plug Wrench Size | 13/16 inch |
| Standard Idle Speed | 1,400 ± 150 rpm |
| Valve Clearance (cold) | IN: 0.15 ± 0.02 mm; EX: 0.20 ± 0.02 mm |
| Recommended Battery (electric starter types) | 12 V – 18 Ah to 12 V – 30 Ah |
| Max. Compressed Air for Paper Filter Cleaning | 207 kPa (2.1 kgf/cm², 30 psi) |
| High Altitude Threshold | Carburetor modification recommended above 1,500 m (5,000 ft) |
| Power Loss with Altitude | Approx. 3.5% per 300 m (1,000 ft), even with modified carburetor |
Honda GX340 Engine Details
The Honda GX340 is a commercial-grade engine that commonly powers generators and other equipment. The owner's manual covers the GX240, GX270, GX340 and GX390 together, and it tells owners to treat it as a permanent part of the engine. Because the GX340 is mounted in equipment built by other manufacturers, controls such as the throttle and choke can be engine-mounted or remote-mounted. Owners should also read the instructions supplied by the equipment maker.
A key protective feature on applicable types is the Oil Alert system. It automatically stops the engine before the oil level in the crankcase drops below a safe limit, and the engine switch stays in the ON position. If the engine shuts down and won't restart, check the oil level first. Electric-start types also have a circuit protector for the battery charging circuit. A green indicator pops out when it trips, and the button is pushed to reset it.
Starting is simple. Open the fuel valve, close the choke for a cold start, set the throttle about 1/3 of the way from MIN toward MAX, and turn the engine switch ON. On recoil models, pull the starter grip lightly until you feel resistance, then pull briskly. On electric-start models, hold the key in START for no more than 5 seconds, then wait 10 seconds before trying again so the starter motor doesn't overheat.
The engine can be fitted with several air cleaner designs: a standard dual-filter element, a cyclone dual-filter, an oil-bath type, a single-filter element and a low-profile type. Clean foam elements in warm soapy water or non-flammable solvent, then dip them in clean engine oil and squeeze out the excess. Never brush paper elements. Tap them on a hard surface or blow compressed air through them from the inside.
The maintenance schedule calls for an oil change after the first month or 20 hours, then every 6 months or 100 hours. Clean the air cleaner every 3 months or 50 hours, and the spark arrester every 100 hours. Clean the combustion chamber every 500 hours and check the fuel tube every 2 years. On cyclone-type filters, service intervals extend to 150 hours, and the paper element is replaced every 600 hours.
For storage, the manual recommends adding a fuel stabilizer and running the engine for 10 minutes, or draining the tank and carburetor through the drain bolt. Then pour 5–10 cc of clean oil into the cylinder and pull the starter slowly until the notch on the pulley lines up with the hole in the cover. This closes the valves and keeps moisture out. Recharge the battery once a month during storage.
On electric-start versions, a fuse in the engine switch box protects the starter relay and charging circuits. If the fuse blows, you can still start the engine manually, but the battery won't charge. A spark arrester may be standard or optional, and some areas legally require one. Holes in the throttle and choke levers accept remote control cables. If you use a flexible braided cable, add a return spring.
A carburetor modified for high altitude must be returned to factory settings before running below 1,500 meters. Otherwise the lean mixture can cause overheating and serious engine damage.
Frequently Asked Questions (FAQs)
Can't find the answer you need? Here are some frequently asked questions about the Honda GX340 Engine, and we answer them below.
