Briggs and Stratton 331877

Briggs and Stratton 331877The Briggs and Stratton 331877 Intek Plus Platinum is a 540 cc (32.9 cu·in) single-cylinder air-cooled four-stroke internal combustion gasoline engine, manufactured by Briggs and Stratton.

The B&S 331877 engine has an OHV (overhead) design and a vertical PTO shaft. This engine is equipped with float type carburetor, pulse type fuel pump and an electronic ignition system. The B&S 331877 engine used a paper air filter with a foam pre-cleaner. It is equipped with an electric starter (12V).

The cylinder bore is 94.0 mm (3.7 in) and the piston stroke is 77.8 mm (3.06 in). This engine produced 21.4 PS (15.7 KW; 21.0 HP) at 3,600 rpm of horsepower.

The breakdown of the engine code is as follows:

  • 33 – Displacement
  • 1 – Basic design series
  • 8 – Vertical PTO-shaft
  • 7 – Plain bearing, Pressure lubrication
  • 7 – Electric starter

General information

Engine Specifications
Model B&S 331877 Intek Plus Platinum
Type 4-stroke, OHV, single-cylinder
Displacement 540 cm 3 (32.9 cu-in)
Max. horsepower 21.4 PS (15.7 KW; 21.0 HP) at 3,600 rpm
Max. torque
Fuel system Float type carburetor
Cooling system Forced-air
Ignition system Electronic
Lubricating system Full pressure
Starting system Electric starter
Fuel used Gasoline
Fuel tank capacity

Cylinder Block and Head

Cylinder block
Bore x Stroke 94.0 mm X 77.8 mm (3.70 x 3.06 in)
Sleeve internal diameter 94.010-94.110 mm (3.7012-3.7051 in)
Number of piston rings (compression / oil): 2 / 1
Side clearance Top 0.051-0.076 mm (0.002-0.003 in)
Second 0.051-0.076 mm (0.002-0.003 in)
Oil 0.051-0.076 mm (0.002-0.003 in)
Ring end gap Top 0.150-0.250 mm (0.0059-0.0098 in)
Second 0.300-0.510 mm (0.0118-0.0201 in)
Oil 0.510-0.630 mm (0.0201-0.0248 in)
Connecting rod small end ID 15.890-15.920 mm (0.6256-0.6268 in)
Piston pin outer diameter 15.850-15.890 mm (0.624-0.6256 in)
Cylinder Head
Valve Arrangement: OHV (overhead)
Valves: 2
Valve steam diameter INTAKE 5.920-5.970 mm (0.233-0.235 in)
EXHAUST 5.920-5.970 mm (0.233-0.235 in)

Tightening torque specs

Tightening torque specs
Air cleaner base 6.0 Nm; 4.4 ft·lb
Alternator 2.0 Nm; 1.5 ft·lb
Armature 3.0 Nm; 2.2 ft·lb
Blower housings 10.0 Nm; 7.4 ft·lb
Breather 3.0 Nm; 2.2 ft·lb
Carburetor to intake manifold 8.0 Nm; 5.9 ft·lb
Carburetor solenoid 5.0 Nm; 3.7 ft·lb
Connecting rod 17.0 Nm; 12.6 ft·lb
Control bracket 5.0 Nm; 3.7 ft·lb
Crankcase sump 25.0 Nm; 18.5 ft·lb
Cylinder head 25.0 Nm; 18.5 ft·lb
Cylinder shield 5.0 Nm; 3.7 ft·lb
Exhaust manifold / adapter 19.0 Nm; 14.0 ft·lb
Flywheel nut 135.0 Nm; 100.0 ft·lb
Flywheel fan 16.0 Nm; 11.9 ft·lb
Fuel pump 10.0 Nm; 7.4 ft·lb
Governor lever nut 5.0 Nm; 3.7 ft·lb
Intake manifold to cylinder head 10.0 Nm; 7.4 ft·lb
Muffler 10.0 Nm; 7.4 ft·lb
Oil drain plug 11.0 Nm; 8.1 ft·lb
Oil fill tube 10.0 Nm; 7.4 ft·lb
Oil pump cover 10.0 Nm; 7.4 ft·lb
Regulator / Rectifier 5.0 Nm; 3.7 ft·lb
Rewind starter 3.0 Nm; 2.2 ft·lb
Rocker ball set screw or nut 5.0 Nm; 3.7 ft·lb
Rocker cover 7.0 Nm; 5.2 ft·lb
Starter motor 16.0 Nm; 11.9 ft·lb

Service Information

Max speed 3,600 rpm
Valve clearance
Intake valve clearance 0.08-0.13 mm (0.003-0.005 in)
Exhaust valve clearance 0.13-0.18 mm (0.005-0.007 in)
Oil system
Oil type API SF, SG, SH, SJ or higher
Recommended oil Summer: SAE 30, 10W-30
Winter: SAE 5W-30
Oil capacity (with filter) 1.40 L (1.48 US. qt, 1.23 Imp. qt.)
Ignition system
Spark plug Champion RC12YC
Spark plug gap 0.7-0.8 mm (0.0276-0.0315 in)
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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  1. Thanks for having all of this information in one place. This was very helpful and much appreciated.

  2. Thank you very much for this specific info on my engine. The B&S web info is very vague and not specific to a unique engine. Very helpful and much appreciated.

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