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Yanmar 2T72 Engine

The Yanmar 2T72 is a compact, vertical, two-cylinder, four-cycle, liquid-cooled diesel engine engineered primarily for agricultural machinery, compact utility tractors like the Yanmar YM1100, and light industrial applications. Known for its high power density, exceptional fuel efficiency, and heavy-duty structural durability, the engine features a naturally aspirated design with a cast-iron cylinder block and individual cylinder liners. It is favored by field mechanics for its straightforward, mechanical design that minimizes maintenance overhead and provides reliable long-term service under heavy operating loads.

The cylinder head layout utilizes a traditional Overhead Valve (OHV) configuration. It features two valves per cylinder (one intake valve and one exhaust valve) aligned vertically. The valve train is mechanically driven by a gear-driven camshaft located within the lower cylinder block, transferring motion via solid pushrods and adjustable rocker arm assemblies. The internal cylinder geometry features a nominal bore diameter of 72.0 mm and a stroke length of 78.6 mm. Total engine displacement measures 638 cc. The pistons are configured with a standard three-ring architecture consisting of two compression rings and one specialized oil control ring to maintain optimal compression and limit lubricating oil consumption.

The fuel system utilizes an indirect injection mechanical design featuring a dedicated, inline multi-plunger fuel injection pump. Fuel is drawn from the fuel tank through a primary fuel filter and water separator assembly before entering the injection pump's gallery. The injection pump pressurizes the fuel and delivers it sequentially via high-pressure steel lines to the mechanical fuel injection valves (nozzles) mounted in the cylinder head pre-combustion chambers. Engine speed and fuel metering are controlled automatically by a mechanical flyweight governor assembly integrated directly into the gear housing. Cold starting is assisted by an intake manifold glow plug or a dedicated thermostart system.

Lubrication is managed via a forced pressure feed lubrication system driven by an internal, engine-powered oil pump. The pump draws lubricating oil from the lower oil sump through an inlet strainer, forcing pressurized oil to the main crankshaft bearings, connecting rod journals, and upward through oil passages to the rocker arm shaft assembly. The system incorporates a full-flow, spin-on TracPartz Yanmar Oil Filter alongside an internal oil pressure relief valve to safeguard the system against extreme pressure spikes.

The cooling architecture relies on a forced liquid circulation cooling system. A belt-driven centrifugal water pump continuously circulates coolant through the internal jackets of the cylinder block and cylinder head to absorb combustion heat. A wax-pellet style thermostat controls flow orientation: restricting flow during warmup and fully opening to redirect hot coolant through an external radiator equipped with a pusher or puller cooling fan once optimal operating temperature is reached.

General Technical Data

Engine Specifications

Engine Model ............... Yanmar 2T72
Engine Type ............... 4-cycle inline 2-cylinder liquid-cooled diesel
Number of Cylinders ............... 2
Cylinder Arrangement ............... In-line vertical
Engine Bore, in (mm) ............... 2.83 (72.0)
Engine Stroke, in (mm) ............... 2.83 (72.0)
Displacement, cu.in (L) ............... 35.9 (0.589)
Rated Engine Power, hp (kW) ............... 11.5-13.0 (8.6-9.7)
Rated Engine Speed, rpm ............... 2400-2800
Peak Torque ............... 23.6-26.5 lb-ft (32.0-36.0 Nm) at 1800-2000 rpm
Idle Speed ............... 800-900 rpm
Aspiration Type ............... Naturally Aspirated
Operating Speed ............... 2400 rpm
Compression Ratio ............... 22.5:1-23.5:1
Firing Order ............... 1-2
Combustion Chamber ............... Swirl pre-combustion chamber type
Rotation Direction ............... Counterclockwise from flywheel end
Piston Material ............... High-silicon aluminum alloy
Crankshaft Material ............... Forged alloy steel induction hardened
Crankcase Ventilation ............... Closed circuit breather valve
Cylinder Block Type ............... Cast iron mono-block
Cylinder Head Type ............... Cast iron single piece
Lubrication System ............... Full forced pressure trochoid pump
Oil Pump Type ............... Trochoid gear-driven pump
Oil Filter Type ............... Full-flow spin-on cartridge
Cooling System ............... Liquid-cooled with radiator
Water Pump Type ............... Belt-driven centrifugal impeller pump
Air Cleaner Type ............... Dry polyurethane element type
Starting System ............... Electric starter motor with glow plug
Electrical System ............... 12V
Alternator Capacity ............... 15A

Fuel System

Fuel Injection Pump Type ............... Bosch type inline YPF-M mini pump
Fuel Injector Nozzle Type ............... Throttle type nozzle piece
Fuel Injection Pressure, psi (bar) ............... 1990-2130 (137.0-147.0)
Fuel Feed Pump Type ............... Mechanical diaphragm type pump
Fuel Filter Type ............... Paper element cartridge with water separator
Fuel Specifications ............... ASTM D975 No. 2-D diesel oil
Governor Type ............... Mechanical centrifugal all-speed governor
Injection Timing, deg ............... 18-20 deg BTDC
Fuel Line Diameter, in (mm) ............... 0.23 (6.0)
Maximum Fuel Return Temperature, F (C) ............... 140 (60.0)
Plunger Diameter, in (mm) ............... 0.21 (5.5)
Plunger Stroke, in (mm) ............... 0.27 (7.0)
Delivery Valve Opening Pressure, psi (bar) ............... 426 (29.4)
Nozzle Pintle Diameter, in (mm) ............... 0.039 (1.0)
Nozzle Valve Seat Angle, deg ............... 60 deg

Dimensions and Weight

Overall Length, in (mm) ............... 16.5 (420)
Overall Width, in (mm) ............... 16.8 (425)
Overall Height, in (mm) ............... 19.1 (485)
Dry Weight, lbs (kg) ............... 146 (66)
Wet Weight, lbs (kg) ............... 159 (72)

Maintenance Data

Service Information

Compression Pressure (Minimum), psi (bar) ............... 398 (27.5)
Compression Pressure Between Cylinders, psi (bar) ............... 42.6 (2.9)
Oil Pressure at Low Idle, psi (bar) ............... 8.5 (0.6)
Oil Pressure at Rated Speed, psi (bar) ............... 42.6-56.8 (2.9-3.9)
Radiator Cap Opening Pressure, psi (bar) ............... 12.8 (0.9)
Coolant Operating Temperature Range, F (C) ............... 167-194 (75.0-90.0)
Thermostat Opening Temperature, F (C) ............... 160 (71.0)
Thermostat Full Open Temperature, F (C) ............... 185 (85.0)
Fan Belt Tension Deflection, in (mm) ............... 0.39-0.55 (10.0-14.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.0078 (0.20)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.0078 (0.20)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, SAE 10W-30, or 15W-40
API Service Classifications ......................... CD or CE
Engine Oil Capacity with Filter, qt (L) ............... 2.1 (2.0)
Engine Oil Capacity without Filter, qt (L) ............... 1.9 (1.8)
Coolant System Fluid Capacity, qt (L) ............... 2.3 (2.2)

Service Intervals

Change oil and filter ............... Every 200 hours
Inspect air cleaner ............... Every 50 hours
Replace air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 250 hours
Valve clearance adjustment ............... Every 300 hours
Fuel system inspection ............... Every 300 hours
Change coolant ............... Every 1000 hours
Compression test ............... Every 500 hours
Clean radiator core ............... Every 200 hours
Inspect belt tension ............... Every 100 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 2.8346-2.8354 (72.000-72.020)
Cylinder Bore Wear Limit, in (mm) ............... 2.8425 (72.200)
Cylinder Bore Out-of-Round, in (mm) ............... 0.0007 (0.020)
Cylinder Bore Taper Limit, in (mm) ............... 0.0011 (0.030)
Cylinder Head Surface Flatness Distortion, in (mm) ............... 0.0019 (0.050)
Cylinder Block Deck Surface Distortion, in (mm) ............... 0.0019 (0.050)
Crankshaft Journal Outer Diameter, in (mm) ............... 1.7716-1.7722 (45.000-45.015)
Crankpin Outer Diameter, in (mm) ............... 1.5748-1.5753 (40.000-40.013)
Crankshaft End Play, in (mm) ............... 0.0035-0.0094 (0.09-0.24)
Main Bearing Oil Clearance, in (mm) ............... 0.0015-0.0033 (0.04-0.08)
Connecting Rod Bearing Clearance, in (mm) ............... 0.0013-0.0031 (0.03-0.08)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.7881-0.7889 (20.017-20.036)
Connecting Rod Big End I.D, in (mm) ............... 1.6929-1.6937 (43.000-43.020)
Piston Outer Diameter, in (mm) ............... 2.8315-2.8326 (71.920-71.950)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.0023-0.0035 (0.060-0.090)
Piston Pin Outer Diameter, in (mm) ............... 0.7872-0.7876 (19.995-20.005)
Piston Pin to Piston Boss Clearance, in (mm) ............... 0.0003-0.0007 (0.009-0.018)
Piston Pin to Small End Bushing Clearance, in (mm) ............... 0.0005-0.0014 (0.012-0.036)
Top Ring Groove Width, in (mm) ............... 0.0799-0.0807 (2.030-2.050)
Second Ring Groove Width, in (mm) ............... 0.0791-0.0799 (2.010-2.030)
Oil Ring Groove Width, in (mm) ............... 0.1578-0.1586 (4.010-4.030)
Top Ring Side Clearance, in (mm) ............... 0.0023-0.0037 (0.06-0.09)
Second Ring Side Clearance, in (mm) ............... 0.0019-0.0033 (0.05-0.08)
Oil Ring Side Clearance, in (mm) ............... 0.0011-0.0027 (0.03-0.07)
Top Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.20-0.35)
Second Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.20-0.35)
Oil Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.15-0.30)
Intake Valve Guide Inner Diameter, in (mm) ............... 0.2755 (7.000)
Exhaust Valve Guide Inner Diameter, in (mm) ............... 0.2755 (7.000)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2736-0.2742 (6.950-6.965)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2724-0.2732 (6.920-6.940)
Intake Valve Seat Angle, deg ............... 45
Exhaust Valve Seat Angle, deg ............... 45
Valve Seat Width, in (mm) ............... 0.0551-0.0629 (1.400-1.600)
Valve Margin Thickness, in (mm) ............... 0.039 (1.0)
Valve Spring Free Length, in (mm) ............... 1.496 (38.0)
Camshaft Journal Outer Diameter (Front), in (mm) ............... 1.5716-1.5724 (39.920-39.940)
Camshaft Journal Outer Diameter (Rear), in (mm) ............... 1.5716-1.5724 (39.920-39.940)
Cam Lobe Height (Intake), in (mm) ............... 1.3346-1.3393 (33.900-34.020)
Cam Lobe Height (Exhaust), in (mm) ............... 1.3346-1.3393 (33.900-34.020)
Camshaft Journal Oil Clearance, in (mm) ............... 0.0019-0.0037 (0.05-0.09)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4716-0.4721 (11.980-11.992)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.4726-0.4737 (12.005-12.035)
Rocker Arm Bushing to Shaft Clearance, in (mm) ............... 0.0005-0.0021 (0.013-0.055)
Tappet Body Outer Diameter, in (mm) ............... 0.8251-0.8259 (20.960-20.980)
Tappet Guide Hole Inner Diameter, in (mm) ............... 0.8267-0.8275 (21.000-21.021)
Idler Gear Shaft Outer Diameter, in (mm) ............... 1.4551-1.4559 (36.960-36.980)
Idler Gear Bushing Inner Diameter, in (mm) ............... 1.4568-1.4576 (37.000-37.025)
Idler Gear Bushing Oil Clearance, in (mm) ............... 0.0009-0.0025 (0.025-0.065)

Tightening Torques

Cylinder Head Bolts, lb-ft (Nm) ............... 50.6-54.2 (68.6-73.5)
Connecting Rod Cap Bolts, lb-ft (Nm) ............... 23.1-25.3 (31.4-34.3)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 39.7-43.3 (53.9-58.8)
Flywheel Retaining Bolts, lb-ft (Nm) ............... 57.8-61.4 (78.4-83.3)
Crankshaft V-Pulley Nut, lb-ft (Nm) ............... 83.1-90.4 (112.7-122.5)
Camshaft Thrust Plate Bolts, lb-ft (Nm) ............... 14.4-18.0 (19.6-24.5)
Rocker Shaft Support Bracket Bolts, lb-ft (Nm) ............... 17.3-20.2 (23.5-27.4)
Cylinder Head Cover Cap Nuts, lb-ft (Nm) ............... 4.3-5.7 (5.9-7.8)
Oil Pan Mounting Perimeter Bolts, lb-ft (Nm) ............... 6.5-8.6 (8.8-11.7)
Oil Pan Drain Plug Fitting Bolt, lb-ft (Nm) ............... 36.1-43.3 (49.0-58.8)
Timing Gear Case Cover Fasteners, lb-ft (Nm) ............... 6.5-8.6 (8.8-11.7)
Flywheel Housing Back Plate Bolts, lb-ft (Nm) ............... 36.1-43.3 (49.0-58.8)
Fuel Injection Pump Delivery Valve Holder, lb-ft (Nm) ............... 25.3-28.9 (34.3-39.2)
Fuel Injection Pump Mounting Flange Nuts, lb-ft (Nm) ............... 14.4-18.0 (19.6-24.5)
Fuel Injector Assembly Nozzle Holder Body, lb-ft (Nm) ............... 43.3-50.6 (58.8-68.6)
Fuel Injector Retaining Bracket Nuts, lb-ft (Nm) ............... 17.3-20.2 (23.5-27.4)
High Pressure Fuel Line Flare Nuts, lb-ft (Nm) ............... 18.0-21.7 (24.5-29.4)
Fuel Filter Bracket Mating Bolts, lb-ft (Nm) ............... 14.4-18.0 (19.6-24.5)
Glow Plug Main Hex Body, lb-ft (Nm) ............... 10.8-14.4 (14.7-19.6)
Glow Plug Electrical Wiring Terminal Nut, lb-ft (Nm) ............... 0.7-1.0 (1.0-1.4)
Oil Pressure Switch Sensor Unit, lb-ft (Nm) ............... 8.6-11.5 (11.7-15.6)
Coolant Temperature Sender Sensor, lb-ft (Nm) ............... 18.0-21.7 (24.5-29.4)
Water Pump Assembly Mounting Stud Nuts, lb-ft (Nm) ............... 14.4-18.0 (19.6-24.5)
Cooling Fan Pulley Set Center Nut, lb-ft (Nm) ............... 21.7-25.3 (29.4-34.3)
Exhaust Manifold Runner Mounting Nuts, lb-ft (Nm) ............... 17.3-20.2 (23.5-27.4)
Intake Manifold Runner Mounting Bolts, lb-ft (Nm) ............... 14.4-18.0 (19.6-24.5)
Air Cleaner Bracket Support Bolts, lb-ft (Nm) ............... 14.4-18.0 (19.6-24.5)
Starter Motor Mounting Flange Fasteners, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Alternator Pivot Support Hinge Bolt, lb-ft (Nm) ............... 25.3-32.5 (34.3-44.1)
Alternator Slotted Tension Adjuster Bolt, lb-ft (Nm) ............... 10.8-14.4 (14.7-19.6)
Exhaust Pipe Silhouette Silencer Flange Nut, lb-ft (Nm) ............... 17.3-20.2 (23.5-27.4)
Oil Pressure Relief Valve Plug Bolt, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Idler Gear Shaft Core Retention Bolt, lb-ft (Nm) ............... 17.3-20.2 (23.5-27.4)
Oil Pipe Union Banjo Bolts (M8), lb-ft (Nm) ............... 11.5-14.4 (15.6-19.6)
Oil Pipe Union Banjo Bolts (M10), lb-ft (Nm) ............... 17.3-21.7 (23.5-29.4)
Breather Valve Chamber Cover Screws, lb-ft (Nm) ............... 2.1-2.8 (2.9-3.9)
Engine Mount Base Feet Frame Bolts, lb-ft (Nm) ............... 36.1-43.3 (49.0-58.8)
Stop Solenoid Assembly Body, lb-ft (Nm) ............... 10.8-14.4 (14.7-19.6)
Fuel Feed Pump Lever Cam Housing Screws, lb-ft (Nm) ............... 5.7-7.2 (7.8-9.8)

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