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Honda GX340 Maintenance

Engine Model: Honda GX340
Engine Type: 4-cycle overhead valve 1-cylinder air-cooled gasoline engine
Total Displacement: 20.6 cu.in (337 cc)
Rated Engine Power: 11 Hp (8.2 kW) at 3600 rpm
Fuel System: Horizontal carburetor with butterfly valve

Service Data

Cylinder Bore Inside Diameter (Maximum), in (mm) .............. 3.235 (82.170)
Cylinder Compression, psi (kPa) .............. 85-121 (600-850)
Cylinder Head (Max Out of Flatness), in (mm) .............. 0.004 (0.10)
Intake Valve Clearance, in (mm) .............. 0.006 (0.15)
Exhaust Valve Clearance, in (mm) .............. 0.008 (0.20)

Engine Oil and Filter

Engine Oil Type (Summer) .............. SAE 10W-30
Engine Oil Type (Winter) .............. SAE 5W-30
API Service Classifications .............. CC, CD, SG, SF
Oil Capacity, qts (L) .............. 1.16 (1.10)
Air Filter Element Part Number .............. 17210-ZE3-010

Carburetor Adjustment

Main Jet (Externally/Internally Vented Bowl) .............. #98 / #108
Idle Fuel (Externally/Internally Vented Bowl) .............. 2-1/2 turns out / 3 turns out
Float Height, in (mm) .............. 0.52 (13.2)
Low Idle Speed, rpm .............. 1400±150
High Idle Speed, rpm .............. 3850±150

Ignition System

Spark Plug Type .............. NGK BPR6ES or Denso W20EPR-U
Spark Plug Gap, in (mm) .............. 0.028-0.032 (0.70-0.80)
Module Air Gap, in (mm) .............. 0.008-0.024 (0.20-0.60)
Ignition Timing, deg .............. 25 BTDC
Spark Plug Torque, Nm (ft-lbs) .............. 20 (14)

Service Intervals

Check Engine Oil Level .............. Every 10 hours
Clean Air Filter Element .............. Every 50 hours
Change Engine Oil .............. Every 100 hours
Check and Adjust Spark Plug .............. Every 100 hours
Clean Fuel Strainer .............. Every 300 hours
Check and Adjust Idle Speed .............. Every 300 hours
Check Carburetor Adjustment .............. Every 300 hours
Replace Spark Plug .............. Every 300 hours
Replace Air Filter Element .............. Every 300 hours
Check and Adjust Valve Clearance .............. Every 300 hours
Clean Combustion Chamber .............. Every 300 hours
Clean Fuel Line .............. Every 300 hours

Tightening Torques

Crankcase Cover (M8x1.25) .............. 24 Nm (18 ft-lb)
Cylinder Head Cover Bolt (M10x1.25) .............. 35 Nm (25 ft-lb)
Rocker Arm Pivot Bolt (M8x1.25) .............. 24 Nm (18 ft-lb)
Oil Drain Plug Bolt (M12x1.5) .............. 23 Nm (17 ft-lb)
Connecting Rod Bolt (M8x1.25) .............. 14 Nm (10 ft-lb)
Flywheel Nut (M16x1.5) .............. 115 Nm (83 ft-lb)
Air Cleaner Wing Nut (M6x1.0) .............. 10 Nm (7 ft-lb)
Muffler Bolt (M8x1.25) .............. 24 Nm (17 ft-lb)
Oil Level Switch Bolt (M10x1.25) .............. 10 Nm (7 ft-lb)
Fuel Strainer Cup (M24x1.0) .............. 3.9 Nm (2.9 ft-lb)
Spark Plug (M14x1.25) .............. 20 Nm (14 ft-lb)

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