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Mitsubishi K4M Engine

The Mitsubishi K4M is an industrial-grade, vertical, water-cooled, 4-stroke, inline 4-cylinder diesel engine. It is widely deployed in compact construction machinery, agricultural equipment, and specialized industrial tools, including mini-excavators (such as the Hanix S and B 30, Mitsubishi MM57SR, and Pel-Job LS 502), tractors (Mitsubishi EB450, GOZ24, GOZ28), wheel loaders, and skid-steer loaders. Characterized by a heavy-duty, robust cast-iron cylinder block, this engine family is engineered specifically for durability and consistent power delivery in high-load, confined-space industrial applications.

Valve Configuration: Overhead valve (OHV) design featuring 8 valves in total (2 valves per cylinder: 1 intake and 1 exhaust). Bore and Stroke: 84.0 mm bore diameter and 90.0 mm stroke length. Cooling System: Forced liquid-circulation setup operated by a belt-driven centrifugal water pump. The system incorporates an inline thermostat to regulate optimal operational temperatures and an engine-driven cooling fan to draw airflow through an external radiator core.

Fuel System: Mechanical direct or indirect diesel injection system utilizing an inline or distributor-type injection pump linked directly to a mechanical speed governor. Fuel delivery incorporates a dedicated primary water separator, fuel filter assembly, and high-pressure steel lines directing fuel to mechanical multi-hole injectors inside the combustion chamber. Lubrication System: Forced-feed lubrication layout pressurized by a trochoid-type oil pump driven directly via the crankshaft gear. The assembly includes a full-flow spin-on oil filter element and a built-in pressure regulating valve to stabilize oil delivery across various load ranges.

General Technical Data

Engine Specifications

Engine Model ............... Mitsubishi K4M
Engine Type ............... 4-cycle inline 4-cylinder water-cooled diesel
Number of Cylinders ............... 4
Cylinder Arrangement ............... In-line vertical position
Engine Bore, in (mm) ............... 3.31 (84.0)
Engine Stroke, in (mm) ............... 3.54 (90.0)
Displacement, cu.in (L) ............... 121.7 (1.995)
Rated Engine Power, hp (kW) ............... 42.0 (31.3)
Rated Engine Speed, rpm ............... 2200-2500
Peak Torque, lb-ft (Nm) ............... 84.8 (115.0) at 1600-1800 rpm
Idle Speed, rpm ............... 750-850
Maximum No-Load Speed, rpm ............... 2650-2800
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 22.0:1-23.0:1
Firing Order ............... 1-3-4-2
Cylinder Block Type ............... Cast iron monoblock architecture
Cylinder Head Type ............... Cast iron single piece overhead mechanism
Combustion Chamber ............... Swirl chamber indirect injection
Lubrication System ............... Full-pressure feed by trochoid pump
Oil Pump Type ............... Gear-driven trochoid assembly
Oil Filter Type ............... Full-flow, cartridge spin-on mechanism
Cooling System ............... Forced liquid circulation by centrifugal system
Water Pump Type ............... Belt-driven centrifugal impeller
Air Cleaner Type ............... Dry element dual-stage filter
Starting System ............... Electric starter motor with integrated glow plugs
Electrical System, V ............... 12
Starter Motor Power, hp (kW) ............... 2.68 (2.0)
Alternator Capacity, A ............... 40-50

Fuel System

Fuel Injection Pump Type ............... In-line Bosch mini pump or cassette type
Fuel Injection Timing, deg ............... 18.0-20.0 BTDC
Fuel Injection Pressure, psi (bar) ............... 1991.0-2134.0 (137.3-147.1)
Fuel Injector Nozzle Type ............... Throttle type DN0PD series nozzle
Fuel Feed Pump Type ............... Mechanical diaphragm design pump
Fuel Filter Type ............... Spin-on cartridge paper element filter
Fuel Return System Line ............... Overflow pipe connection returning to source reservoir
Injection Line Outer Diameter, in (mm) ............... 0.24 (6.0)
Injection Line Inner Diameter, in (mm) ............... 0.08 (2.0)
Governor Type ............... Mechanical centrifugal weight system
Fuel Tank Minimum Vent Size, in (mm) ............... 0.08 (2.0)
Fuel Leak-Off Line Internal Diameter, in (mm) ............... 0.16 (4.0)
Nozzle Holder Assembly Type ............... Screw-in flange installation assembly
Nozzle Opening Pressure, Initial Setting, psi (bar) ............... 2059.0 (142.0)
Nozzle Opening Pressure, Service Limit, psi (bar) ............... 1849.0 (127.5)

Dimensions and Weight

Overall Length, in (mm) ............... 24.2 (615)
Overall Width, in (mm) ............... 18.7 (475)
Overall Height, in (mm) ............... 24.6 (625)
Dry Weight, lbs (kg) ............... 397 (180)
Wet Weight, lbs (kg) ............... 430 (195)

Maintenance Data

Service Information

Compression Pressure, Standard, psi (bar) ............... 455 (32.1)
Compression Pressure, Limit, psi (bar) ............... 370 (25.5)
Compression Variation Between Cylinders, psi (bar) ............... 36.8 (2.6)
Oil Pressure at Rated Speed, psi (bar) ............... 42.7-56.9 (2.9-3.9)
Oil Pressure at Idle Speed, psi (bar) ............... 14.2 (0.98) or greater
Thermostat Opening Temperature, F (C) ............... 170.6 (77.0)
Thermostat Full Open Temperature, F (C) ............... 194.0 (90.0)
Cooling Fan Belt Deflection, in (mm) ............... 0.39-0.47 (10.0-12.0)
Intake Valve Clearance (Cold), in (mm) ............... 0.0098 (0.25)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.0098 (0.25)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30W, SAE 10W-30, or 5W-20
API Service Classifications ......................... CF or CH-4
Engine Oil Capacity, Total, qt (L) ............... 6.87 (6.5)
Engine Oil Capacity, High Level, qt (L) ............... 5.81 (5.5)
Engine Oil Capacity, Low Level, qt (L) ............... 3.70 (3.5)
Coolant Capacity, Engine Block, qt (L) ............... 2.64 (2.5)
Coolant Capacity, Total System, qt (L) ............... 7.40 (7.0)

Service Intervals

Change oil and filter ............... Every 200 hours
Inspect air cleaner ............... Every 100 hours
Replace air cleaner ............... Every 1000 hours
Replace fuel filter ............... Every 400 hours
Valve clearance adjustment ............... Every 400 hours
Fuel system inspection ............... Every 600 hours
Change coolant ............... Every 1000 hours
Compression test ............... Every 800 hours
Clean radiator core ............... Every 250 hours
Inspect belt tension ............... Every 100 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 3.3071-3.3083 (84.000-84.030)
Cylinder Bore Wear Limit, in (mm) ............... 3.3150 (84.200)
Connecting Rod Small End Bushing I.D, in (mm) ............... 1.1031-1.1039 (28.020-28.040)
Crankshaft Main Journal Outer Diameter, in (mm) ............... 2.2441-2.2449 (57.000-57.020)
Crankpin Journal Outer Diameter, in (mm) ............... 1.8898-1.8906 (48.000-48.020)
Main Bearing Clearance, in (mm) ............... 0.0016-0.0031 (0.040-0.080)
Crankpin Bearing Clearance, in (mm) ............... 0.0014-0.0028 (0.035-0.070)
Crankshaft End Play, in (mm) ............... 0.0020-0.0071 (0.050-0.180)
Piston Outer Diameter, in (mm) ............... 3.3043-3.3055 (83.930-83.960)
Piston to Cylinder Wall Clearance, in (mm) ............... 0.0028-0.0039 (0.070-0.100)
Piston Pin Outer Diameter, in (mm) ............... 1.1024-1.1028 (28.000-28.010)
Piston Pin Bore Diameter, in (mm) ............... 1.1026-1.1030 (28.005-28.015)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0002-0.0006 (0.005-0.015)
Top Ring Side Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Second Ring Side Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Oil Ring Side Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Top Ring End Gap, in (mm) ............... 0.0098-0.0157 (0.250-0.400)
Second Ring End Gap, in (mm) ............... 0.0098-0.0157 (0.250-0.400)
Oil Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Cylinder Head Surface Distortion Flatness, in (mm) ............... 0.0020 (0.050)
Cylinder Block Top Surface Flatness, in (mm) ............... 0.0020 (0.050)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2598-0.2604 (6.600-6.615)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2587-0.2593 (6.570-6.585)
Valve Guide Inner Diameter Standard, in (mm) ............... 0.2614-0.2622 (6.640-6.660)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0010-0.0024 (0.025-0.060)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0022-0.0035 (0.055-0.090)
Valve Seat Angle, deg ............... 45
Valve Face Angle, deg ............... 45
Valve Seat Width, in (mm) ............... 0.0512-0.0709 (1.300-1.800)
Valve Margin Thickness, in (mm) ............... 0.0394 (1.000)
Valve Spring Free Length, in (mm) ............... 1.6929 (43.000)
Camshaft Journal Outer Diameter (№1), in (mm) ............... 1.6535-1.6543 (42.000-42.020)
Camshaft Journal Outer Diameter (№2), in (mm) ............... 1.6142-1.6150 (41.000-41.020)
Camshaft Journal Outer Diameter (№3), in (mm) ............... 1.5748-1.5756 (40.000-40.020)
Camshaft Bearing Bore Inside Diameter (№1), in (mm) ............... 1.6555-1.6567 (42.050-42.080)
Camshaft Bearing Bore Inside Diameter (№2), in (mm) ............... 1.6161-1.6173 (41.050-41.080)
Camshaft Bearing Bore Inside Diameter (№3), in (mm) ............... 1.5768-1.5780 (40.050-40.080)
Camshaft Journal Bearing Clearance, in (mm) ............... 0.0012-0.0031 (0.030-0.080)
Camshaft Lobe Height (Intake), in (mm) ............... 1.4370-1.4390 (36.500-36.550)
Camshaft Lobe Height (Exhaust), in (mm) ............... 1.4370-1.4390 (36.500-36.550)
Camshaft End Play, in (mm) ............... 0.0020-0.0059 (0.050-0.150)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4717-0.4724 (11.980-12.000)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.4732-0.4740 (12.020-12.040)
Rocker Arm Bushing to Shaft Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Tappet Outer Diameter, in (mm) ............... 0.7071-0.7079 (17.960-17.980)
Tappet Guide Hole Inner Diameter, in (mm) ............... 0.7087-0.7095 (18.000-18.020)
Tappet to Guide Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)

Tightening Torques

Cylinder Head Bolts, lb-ft (Nm) ............... 54.2-57.9 (73.5-78.5)
Connecting Rod Cap Nuts, lb-ft (Nm) ............... 23.1-25.3 (31.4-34.3)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 36.2-39.8 (49.0-53.9)
Flywheel Fastening Bolts, lb-ft (Nm) ............... 61.5-65.1 (83.4-88.3)
Crankshaft Pulley Center Bolt, lb-ft (Nm) ............... 72.3-79.6 (98.0-107.9)
Camshaft Thrust Plate Retention Bolt, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Rocker Stay Support Anchor Bolt, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Rocker Arm Adjusting Screw, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Valve Mechanism Cover Acorn Nuts, lb-ft (Nm) ............... 3.6-5.1 (4.9-6.9)
Timing Gear Case Cover Fastener Bolt, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Oil Pan Mounting Perimeter Flange Bolt, lb-ft (Nm) ............... 7.2-8.7 (9.8-11.8)
Oil Pan Sump Drain Plug, lb-ft (Nm) ............... 25.3-32.5 (34.3-44.1)
Oil Pressure Regulator Valve Plug, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Oil Pump Assembly Retention Fixing Bolt, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Water Pump Flange Retaining Bolt, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Thermostat Housing Attachment Stud Bolt, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Fuel Injection Pump Delivery Valve Holder, lb-ft (Nm) ............... 25.3-28.9 (34.3-39.2)
Fuel Injection Pump Flange Nut Mounting, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Fuel Injection Pump Coupling Drive Gear Nut, lb-ft (Nm) ............... 28.9-36.2 (39.2-49.0)
Fuel Injector Nozzle Holder Assembly to Head, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Fuel Injector Retaining Cap Nut Outer, lb-ft (Nm) ............... 25.3-28.9 (34.3-39.2)
Fuel High Pressure Line Union Nut, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Leak-Off Return Tube Header Nut, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Glow Plug Primary Hex Body, lb-ft (Nm) ............... 11.0-14.5 (14.9-19.6)
Glow Plug Electrical Harness Terminal Nut, lb-ft (Nm) ............... 1.1-1.4 (1.5-1.9)
Starter Motor Frame Mounting Flange Bolt, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Alternator Pivot Adjustment Lock Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Exhaust Manifold Heat Shield Retaining Bolt, lb-ft (Nm) ............... 7.2-8.7 (9.8-11.8)
Exhaust Manifold to Cylinder Head Stud Nut, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Inlet Manifold to Cylinder Head Fixing Bolt, lb-ft (Nm) ............... 11.0-14.0 (14.9-19.0)
Flywheel Housing to Cylinder Block Bolt, lb-ft (Nm) ............... 36.2-43.4 (49.0-58.8)
Oil Pressure Sensor Indicator Switch, lb-ft (Nm) ............... 11.0-14.5 (14.9-19.6)
Coolant Temperature Sender Device Plug, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)

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• Mitsubishi Engines Specs
  
• Mitsubishi K4C Specs
  
• Mitsubishi K4D Specs
  
• Mitsubishi K4E Specs
  
• Mitsubishi K4F Specs
  
• Mitsubishi K4N Specs
  

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