Honda GC135

Honda GC135 engineThe Honda GC135 is a small (135 cc) single-cylinder air-cooled 4-stroke internal combustion gasoline engine with horizontal shaft, manufactured by Honda Motor Company since 1997 for general-purpose applications.

This engine has a single-cylinder, compact combustion chamber, tough resin overhead cam for durability and quietness and uniblock construction reduce fuel consumption. The Honda GC135 engine has transistorized magneto ignition, horizontal type carburetor, and recoil starter.

A 64 mm (2.5 in) cylinder bore and 42 mm (1.7 in) piston stroke give the engine a total of 135 cc of displacement. Compression ratio is 8.5:1. It produces 2.9 kW (4.0 HP) at 3,600 rpm and 8.6 N·m (0.88 kg·m, 6.4 ft·lb) of torque at 2,500 rpm.

General information

Engine Specifications
Model GC135
Type 4-stroke, OHC, single cylinder
Displacement 135 cm 3 (8.2 cu-in)
Max. horsepower 4.0 HP (2.9 kW) at 3,600 rpm
Max. torque (crank PTO) 8.6 N·m (0.88 kg·m, 6.4 ft·lb) at 2,500 rpm
Carburetor Horizontal type, butterfly valve
Cooling system Forced-air
Ignition system Transistorized magneto ignition
Lubricating system Splash
Starting system Recoil starter
Stoping system Ignition primary circuit ground
Fuel used Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity 1.7 l (0.45 US. Gal, 0.37 Imp. Gal.)
Fuel consumption 230 g/HPh
PTO shaft rotation Counterclockwise (from PTO shaft side)

Dimensions and Weight

S Q W V P
Length, mm (in) 321 (12.6) 330 (13.0) 347 (13.7) 340 (13.4) 330 (13.0)
Width, mm (in) 369 (14.5)
Height, mm (in) 315 (12.4)
Dry weight, kg (lb) 11.2 (24.7)
Operating
weight, kg (lb)		 13.0 (28.7)

Cylinder Block and Head

Cylinder block
Compression ratio: 8.5:1
Bore x Stroke 64 mm X 42 mm (2.5 x 1.7 in)
Sleeve internal diameter 64.00 mm (2.52 in)
Piston skirt outer diameter 63.969 mm (2.5185 in)
Number of piston rings (compression / oil): 2 / 1
Ring side clearance Top/second/oil 0.015-0.045 mm (0.0006-0.0018 in)
Ring end gap Top 0.20-0.35 mm (0.008-0.014 in)
Second 0.30-0.45 mm (0.012-0.018 in)
Oil 0.15-0.35 mm (0.006-0.014 in)
Ring width Top/second 1.5 mm (0.06 in)
Oil 2.5 mm (0.10 in)
Connecting rod small end ID 13.005 mm (0.512 in)
Connecting rod big end ID 26.02 mm (1.024 in)
Crankpin outer diameter 25.98 mm (1.023 in)
Main journal outer diameter PTO side 27.993 mm (1.1021 in)
Flywheel side 25.393 mm (0.9997 in)
Cylinder Head
Warpage (limit) 0.10 mm (0.004 in)
Valve Arrangement: OHC
Valves: 2
Stem outer diameter (standard): INTAKE 5.480 mm (0.216 in)
EXHAUST 5.44 mm (0.214 in)
Guide internal diameter INTAKE / EXHAUST 5.5 mm (0.2165 in)
Spring free length 34.0 mm (1.34 in)

Tightening torque specs

Tightening torque specs
Air cleaner case bolt 10 Nm; 1.0 kg·m; 7 ft·lb
Crankcase cover bolt 12 Nm; 1.2 kg·m; 8.6 ft·lb
Connecting rod bolt 12 Nm; 1.2 kg·m; 8.6 ft·lb
Valve adjusting lock nut 8 Nm; 0.8 kg·m; 5.8 ft·lb
Cylinder head cover bolt 12 Nm; 1.2 kg·m; 8.6 ft·lb
Oil drain plug bolt 24 Nm; 2.4 kg·m; 17 ft·lb
Flywheel nut 52 Nm; 5.3 kg·m; 38 ft·lb
Governor arm nut 10 Nm; 1.0 kg·m; 7 ft·lb
Muffler bolt 12 Nm; 1.2 kg·m; 8.6 ft·lb
Recoil starter nut 8.5 Nm; 0.85 kg·m; 6.1 ft·lb
Fan cover stud bolt 12 Nm; 1.2 kg·m; 8.6 ft·lb
Fuel tank bolt, nut 10 Nm; 1.0 kg·m; 7 ft·lb
Spark plug 20 Nm; 2.0 kg·m; 14 ft·lb
Others
5 mm bolts, nuts 5.5 Nm; 0.55 kg·m; 4.0 ft·lb
6 mm bolts, nuts 10 Nm; 1.0 kg·m; 7 ft·lb
8 mm bolts, nuts 24 Nm; 2.4 kg·m; 17 ft·lb
10 mm bolts, nuts 37 Nm; 3.7 kg·m; 27 ft·lb
12 mm bolts, nuts 55 Nm; 5.5 kg·m; 39.5 ft·lb

Service Information

Engine
Maximum speed 3,850 ± 150 rpm
Idle speed 1,400 ± 150 rpm
Cylinder compression 5.0 kg/cm2 (71 psi) at 600 rpm
Valve clearance
Intake valve 0.15 ± 0.04 (0.006 ± 0.002)
Exhaust valve 0.20 ± 0.04 (0.008 ± 0.002)
Oil system
Oil type Honda 4-stroke or an equivalent (SE or SF)
Recommended oil SAE 10W-30
Oil capacity 0.58 l (0.61 US. qt, 0.55 Imp. qt.)
Ignition system
Ignition timing 20° B.T.D.C.
Spark plug NGK: BPR6ES
Spark plug gap 0.7-0.8 mm (0.028-0.031 in)
Spark plug torque 20 Nm; 2.0 kg·m; 14 ft·lb
Primary ignition coil resistance 1.0-1.2 kΩ
Secondary ignition coil resistance 10.6-12.8 kΩ
Ignition coil air gap 0.2-0.6 mm (0.008-0.024 in)
Carburetor
Main jet #60
Float height 9.2 mm (0.36 in)
Pilot screw opening 2 turns out
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4 Comments

  1. i have an older gc135 to run a water pump i am having a hard time starting it.Is there an on off switch i am missing there is a push/pull next to the pull cord does that have to be in or out. anything else would be appreciated

    Reply

    • I too have an old GC135, I am not a mechanic and fortunately it starts first pull each time on full choke. There is no on /off switch.

      Reply

    • Firstly try a new spark plug, if that fails then clean the magnets in the flywheel, the valve after a while start to leak so they will have to be ground in again, as the cylinder head is part of the block the only way I found this to be done is to put grinding paste on the valve seat then put the valve in and then fix it in the chuck of a battery powered drill switch it on and gently pull up after a while you will get a new seating, this cured my engine

      Reply

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