Cylinder Head Rebuild Kit
Cylinder Head Rebuild Kit
Cylinder Head Rebuild Kit fits Honda GX340, GX390

Cylinder Head Rebuild Kit fits Honda GX340, GX390

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$ 98.95

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Description Shipping Options Torque Specs & Info Additional Info

Fits Honda Models: 

  • GX340 11hp

  • GX390 13hp 

Includes: 

Cylinder Head Assembled with:

  • Rocker Arms

  • Intake and Exhaust Valves

  • Valve Springs

  • Push Rod Guide Plate

  • Retainer Clips

  • Spark Plug

1x Valve Cover Gasket 

1x Cylinder Head Gasket 

1x Carburetor Gaskets 

2x Muffler Gaskets 

2x Carburetor Stud Mounting Bolts 

4x Cylinder Head Bolts 

1x Valve Cover Bolt 

1x Carburetor Insulator

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Engine Specifications
Model GX390K1
Type 4-stroke, OHV, single cylinder, inclined by 25°
Displacement 389 cm 3 (23.7 cu·in)
Max. horsepower 13.0 HP (10.0 kW) at 3,600 rpm
Max. torque (crank PTO) 27 Nm (2.7 kg·m, 20.0 ft·lb) at 2,500 rpm
Carburetor Horizontal type, butterfly valve
Cooling system Forced-air
Ignition system Transistorized magneto ignition
Lubricating system Forced splash
Starting system Recoil and Starter motor
Stoping system Ignition primary circuit ground
Fuel used Unleaded gasoline (octane number 86 or higher)
Fuel consumption 6.5 Liters (1.72 US gal, 1.43 Imp gal) / h
PTO shaft rotation Counterclockwise (from PTO shaft side)
Honda GX390K1 (Type S)
Length, mm (in) 380 (15.0)
Width, mm (in) 450 (17.7)
Height, mm (in) 443 (17.4)
Dry weight, kg (lb) 31.0
(68.3)
Operating
weight, kg (lb)		 37.0
(81.6)
Cylinder block
Compression ratio: 8.0:1
Bore x Stroke 88 X 64 mm (3.5 x 2.5 in)
Sleeve internal diameter 88.000 mm (3.465 in)
Piston skirt outer diameter 87.985 mm (3.4640 mm)
Number of piston rings (compression / oil): 2 / 1
Ring side clearance Top/second 0.030 – 0.060 (0.0012 – 0.0024)
Ring end gap Top 0.20 – 0.40 mm (0.01 – 0.02 in)
Second 0.20 – 0.40 mm (0.01 – 0.02 in)
Oil (side rail) 0.20 – 0.70 mm (0.01 – 0.03 in)
Ring width Top 2.0 mm (0.08 in)
Second 2.0 mm (0.08 in)
Connecting rod small end I.D. 20.005 mm (0.7876 in)
Connecting rod big end I.D. 36.025 mm (1.4183 in)
Crankshaft outer diameter 35.985 mm (1.4167 in)
Cylinder Head
Warpage (limit) 0.10 mm (0.004 in)
Valve Arrangement: OHV
Valves: 2
Stem outer diameter (standard): INTAKE 6.590 mm (0.2594 in)
EXHAUST 6.550 mm (0.2579 in)
Guide inner diameter: INTAKE/EXHAUST 6.60 mm (0.6260 in)
Cam height: INTAKE 32.40-32.80 mm (1.276-1.291 in)
EXHAUST 31.89-32.29 mm (1.256-1.271 in)
Camshaft outer diameter: 15.984 mm (0.6293 in)
Tightening torque specs
Connecting rod bolt (M8x1.25 Special) 14 Nm; 1.4 kg·m; 10 ft·lb
Cylinder head bolt (M10x1.25) 35 Nm; 3.5 kg·m; 25 ft·lb
Flywheel nut (M16x1.5 Special) 115 Nm; 11.5 kg·m; 83 ft·lb
Rocker arm pivot lock nut (M6x0.5) 10 Nm; 1.0 kg·m; 7 ft·lb
Rocker arm pivot bolt (M8x1.25 Special) 24 Nm; 2.4 kg·m; 17 ft·lb
Crankcase cover bolt (M8x1.25) 24 Nm; 2.4 kg·m; 17 ft·lb
Oil level switch joint nut (M10x1.25) 10 Nm; 1.0 kg·m; 7 ft·lb
Fuel filter joint nut (M10x1.25) 2 Nm; 0.2 kg·m; 1.4 ft·lb
Muffler mounting nut (M8x1.25) 24 Nm; 2.4 kg·m; 17 ft·lb
Air cleaner wing nut (M6x1.0) 9 Nm; 0.9 kg·m; 6.5 ft·lb
Oil drain bolt (M12x1.5) 23 Nm; 2.3 kg·m; 17 ft·lb
Fuel tank bolt (M8x1.25) 24 Nm; 2.4 kg·m; 17 ft·lb
Air cleaner mounting nut (M6x1.0) 10 Nm; 1.0 kg·m; 7 ft·lb
Fuel strainer cup (M24x1.0) 4 Nm; 0.4 kg·m; 2.9 ft·lb
Standard torque values
Bolt, nut (5 mm) 5.5 Nm; 0.55 kg·m; 4.0 ft·lb
Bolt, nut (6 mm) 10 Nm; 1.0 kg·m; 7 ft·lb
Bolt, nut (8 mm) 24 Nm; 2.4 kg·m; 17 ft·lb
Bolt, nut (10 mm) 37.5 Nm; 3.75 kg·m; 27 ft·lb
Bolt, nut (12 mm) 55 Nm; 5.5 kg·m; 40 ft·lb
Engine
Maximum speed 3850 ± 150 rpm
Idle speed 1400 ± 150 rpm
Cylinder compression 6.0-8.5 kg/cm2 (85-121 psi, 0.59 – 0.83 MPa) at 600 rpm
Valve clearance
Intake valve 0.15 ± 0.02 (0.006 ± 0.001)
Exhaust valve 0.20 ± 0.02 (0.008 ± 0.001)
Carburetor
Main jet Externally vented carburetor bowl: #105
Internally vented carburetor bowl: #115
Float height 13.2 mm (0.52 in)
Pilot screw opening Externally vented carburetor bowl: 2-1/2
Internally vented carburetor bowl: 3
Oil system
Oil type Honda 4-stroke or an equivalent (SE or later)
Recommended oil SAE 10W-30
Oil capacity 1.1 L (1.16 US gal, 0.97 lmp qt)
Ignition system
Ignition timing B.T.D.C. 25° (Fixed)
Spark plug NGK: BP6ES, BPR6ES
DENSO: W20EP-U, W20EPR-U
Spark plug gap 0.7-0.8 mm (0.028-0.031 in)
Air gap 0.2-0.6 mm (0.01-0.02 in)
Starter motor
Brush length 7.0 mm (0.28 in) limit: 3.5 mm (0.14 in)
Mica depth 1.0 mm (0.04 in) limit: 0.2 (0.01)

All Honda Models - Torque Specifications & Technical Sheets

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