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Yanmar 2TR20A Engine

The Yanmar 2TR20A (including its specific application variants like the 2TR20A-X or 2TR20A-A) is a heavy-duty, vertical inline two-cylinder diesel engine designed primarily for agricultural machinery and compact utility tractors. It is highly regarded in the workshop environment for its robust cast-iron construction and service longevity. The engine utilizes a 4-stroke cycle with a swirl-type pre-combustion chamber (pre-injection setup) designed to optimize thermal efficiency and provide reliable starting torque under varied load constraints.

The valvetrain features an Overhead Valve (OHV) configuration driven by traditional pushrods and rocker arms. Mechanical actuation relies on a gear-driven camshaft housed within the cylinder block, bypassing the need for timing belts or chains. The setup relies on a standard arrangement of two valves per cylinder (one intake, one exhaust). Bore: 90 mm (3.543 inches). Stroke: 90 mm (3.543 inches). Total Displacement: 1145 cc (1.145 Liters / 69.87 cubic inches). Cylinder Liners: Wet-type replaceable liners.

Fuel delivery utilizes a mechanical inline jerk-type injection pump combined with independent high-pressure fuel lines feeding mechanical injection nozzles. Fuel is drawn from the tank through a primary water separator/sedimenter assembly and a spin-on fuel filter before arriving at the injection pump. A mechanical flyweight governor controls the rack positioning of the pump to sustain engine RPM against varying implement or drivetrain loads. Fuel is directly atomized into the swirl-type pre-combustion chamber to secure optimal ignition properties.

Engine lubrication utilizes a forced-pressure feed system driven by a trochoid or gear-type oil pump located near the governor chamber assembly. Oil is drawn through an internal pickup screen from the oil pan and directed through a full-flow filtration system before distribution to the main bearings, connecting rod journals, and overhead rocker assemblies. Internal detergency and acid-control properties are managed using high-grade 15W-40 or equivalent diesel-service lubricants.

The engine uses a liquid-cooled system featuring an engine-driven water pump that forces coolant through the cylinder block and cylinder head water jackets. Heat dissipation is managed via a heavy-duty front-mounted radiator and a belt-driven cooling fan. Temperature regulation is monitored mechanically through an inline thermostat and an integrated electrical water temperature sending unit/light indicator on the instrument cluster.

General Technical Data

Engine Specifications

Engine Model ............... Yanmar 2TR20A
Engine Type ............... 4-cycle inline 2-cylinder liquid-cooled diesel
Number of Cylinders ............... 2
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.543 (90.0)
Engine Stroke, in (mm) ............... 3.543 (90.0)
Displacement, cu.in (L) ............... 69.87 (1.145)
Rated Engine Power, hp (kW) ............... 20.0-24.0 (14.9-17.9)
Rated Engine Speed, rpm ............... 2400
Peak Torque ............... 46.9 lb-ft (63.6 Nm) at 1800 rpm
Idle Speed ............... 700-800 rpm
Aspiration Type ............... Naturally Aspirated
Operating Speed ............... 2400 rpm
Compression Ratio ............... 20.0:1
Firing Order ............... 1-2
Combustion Chamber ............... Swirl pre-combustion chamber type
Piston Type ............... Aluminum alloy with combustion bowl top surface
Cylinder Liner Type ............... Dry type thin-walled cast iron liner
Main Bearings Number ............... 3 main journal bearings
Camshaft Drive ............... Gear-driven helical train from crankshaft gear
Exhaust System Type ............... Underslung horizontal or vertical silencer manifold
Cylinder Block Type ............... Cast iron mono-block
Cylinder Head Type ............... Cast iron single piece
Lubrication System ............... Full-pressure trochoid pump forced lubrication
Oil Pump Type ............... Trochoid gear-driven
Oil Filter Type ............... Full-flow, spin-on cartridge
Cooling System ............... Liquid-cooled thermosyphon hybrid or centrifugal pump bypass
Water Pump Type ............... Belt-driven, centrifugal
Air Cleaner Type ............... Dry element dual-stage or wet oil bath
Starting System ............... Electric Starter with thermostart plug pre-heater
Electrical System ............... 12V
Alternator Output, A ............... 15-35
Starter Motor Power, hp (kW) ............... 1.9 (1.4)

Fuel System

Fuel Injection Pump Type ............... Bosch type inline jerk multi-plunger pump
Fuel Injection Pump Model ............... Yanmar YP-2 series split plunger config
Fuel Injector Nozzle Type ............... Throttle type pin expansion or pintle style single hole nozzle
Fuel Injection Pressure, psi (bar) ............... 1990-2130 (137-147)
Fuel Delivery Timing, deg BTDC ............... 21.0-23.0
Fuel Feed Pump Type ............... Diaphragm mechanical lever movement off camshaft eccentric lobe
Fuel Filter Type ............... Paper element disposable spin-on container or assembly canister
Fuel Type ............... ASTM D975 No. 2-D ultra low sulfur diesel
Governor Type ............... Mechanical centrifugal all-speed governor
Injection Pump Plunger Diameter, in (mm) ............... 0.236 (6.0)
Injection Pump Stroke, in (mm) ............... 0.275 (7.0)
Nozzle Holder Assembly Type ............... Flange mount dual stud clamp bolt design
Fuel Transfer Pump Lift Height, ft (m) ............... 3.3 (1.0)
Fuel Injection Lines Outer Diameter, in (mm) ............... 0.236 (6.0)
Fuel Injection Lines Inner Diameter, in (mm) ............... 0.078 (2.0)

Dimensions and Weight

Overall Engine Length, in (mm) ............... 22.4 (570)
Overall Engine Width, in (mm) ............... 18.9 (480)
Overall Engine Height, in (mm) ............... 25.6 (650)
Dry Weight Base Engine, lb (kg) ............... 265 (120)
Wet Weight Equipped Engine, lb (kg) ............... 291 (132)

Maintenance Data

Service Information

Compression Pressure, Standard, psi (bar) ............... 400.0-455.0 (27.6-31.4)
Compression Pressure, Limit Minimum, psi (bar) ............... 340.0 (23.4)
Max Compression Pressure Cylinders Variance, psi (bar) ............... 28.4 (1.96)
Relief Valve Pressure Opening, psi (bar) ............... 56.8 (3.92)
Engine Oil Pressure (Cold), psi (bar) ............... 42.6-56.8 (2.94-3.92)
Engine Oil Pressure (Hot), psi (bar) ............... 28.4-42.6 (1.96-2.94)
Minimum Oil Pressure at Idle, psi (bar) ............... 8.5 (0.59)
Radiator Cap Pressure Rating, psi (bar) ............... 7.1-12.8 (0.49-0.88)
Thermostat Opening Temperature, F (C) ............... 160.0 (71.1)
Thermostat Full Open Temperature, F (C) ............... 185.0 (85.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.006 (0.15)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.006 (0.15)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, SAE 10W-30, or SAE 15W-40
API Service Classifications ......................... CC, CD or higher
Engine Oil Capacity with Filter, qt (L) ............... 4.2 (4.0)
Engine Oil Capacity without Filter, qt (L) ............... 3.7 (3.5)
Coolant System Fluid Capacity, qt (L) ............... 4.8 (4.5)

Service Intervals

Change oil and filter ............... Every 100 hours
Inspect air cleaner ............... Every 50 hours
Replace air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 250 hours
Valve clearance adjustment ............... Every 500 hours
Fuel system inspection ............... Every 600 hours
Change coolant ............... Every 1000 hours
Compression test ............... Every 1000 hours
Clean radiator core ............... Every 200 hours
Inspect belt tension ............... Every 100 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 3.5433-3.5441 (90.000-90.022)
Cylinder Bore Wear Maximum Limit, in (mm) ............... 3.5512 (90.200)
Connecting Rod Small End Bushing I.D, in (mm) ............... 1.1031-1.1039 (28.020-28.038)
Crankshaft Main Journal Diameter, in (mm) ............... 2.5582-2.5590 (64.980-65.000)
Main Bearing Shell Thickness, in (mm) ............... 0.0787-0.0791 (2.000-2.010)
Main Bearing Oil Clearance, in (mm) ............... 0.0015-0.0035 (0.038-0.090)
Crankpin Journal Diameter, in (mm) ............... 2.1645-2.1653 (54.980-55.000)
Crankpin Bearing Shell Thickness, in (mm) ............... 0.0590-0.0594 (1.500-1.510)
Crankpin Bearing Oil Clearance, in (mm) ............... 0.0013-0.0031 (0.035-0.080)
Crankshaft Thrust Axial End Play, in (mm) ............... 0.0157 (0.400)
Piston Skirt Outside Diameter, in (mm) ............... 3.5393-3.5401 (89.900-89.920)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.0031-0.0047 (0.080-0.120)
Piston Pin Bore Bushing I.D, in (mm) ............... 1.1024-1.1027 (28.000-28.009)
Piston Pin Outside Diameter, in (mm) ............... 1.1021-1.1023 (27.994-28.000)
Top Ring Groove Width, in (mm) ............... 0.0787-0.0795 (2.000-2.020)
Second Ring Groove Width, in (mm) ............... 0.0787-0.0795 (2.000-2.020)
Third Ring Groove Width, in (mm) ............... 0.0787-0.0795 (2.000-2.020)
Oil Ring Groove Width, in (mm) ............... 0.1575-0.1583 (4.000-4.020)
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)
Third Ring End Gap, in (mm) ............... 0.0098-0.0157 (0.250-0.400)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.200-0.350)
Top Ring Side Clearance, in (mm) ............... 0.0027-0.0041 (0.070-0.105)
Second Ring Side Clearance, in (mm) ............... 0.0019-0.0033 (0.050-0.085)
Oil Ring Side Clearance, in (mm) ............... 0.0011-0.0025 (0.030-0.065)
Cylinder Head Bottom Surface Flatness Warpage, in (mm) ............... 0.0019 (0.050)
Cylinder Block Top Surface Flatness Warpage, in (mm) ............... 0.0019 (0.050)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.3129-0.3137 (7.950-7.970)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.3118-0.3126 (7.920-7.940)
Intake Valve Guide Inside Diameter, in (mm) ............... 0.3149-0.3157 (8.000-8.018)
Exhaust Valve Guide Inside Diameter, in (mm) ............... 0.3149-0.3157 (8.000-8.018)
Intake Valve Stem-to-Guide Clearance, in (mm) ............... 0.0011-0.0026 (0.030-0.068)
Exhaust Valve Stem-to-Guide Clearance, in (mm) ............... 0.0023-0.0038 (0.060-0.098)
Intake Valve Head Recess, in (mm) ............... 0.0236-0.0354 (0.600-0.900)
Exhaust Valve Head Recess, in (mm) ............... 0.0236-0.0354 (0.600-0.900)
Valve Face Angle, deg ............... 45.0
Intake Valve Seat Width, in (mm) ............... 0.0551-0.0669 (1.400-1.700)
Exhaust Valve Seat Width, in (mm) ............... 0.0551-0.0669 (1.400-1.700)
Valve Seat Sinkage Depth, in (mm) ............... 0.0394 (1.000)
Valve Spring Free Length, in (mm) ............... 1.6535 (42.000)
Camshaft Journal Outside Diameter, in (mm) ............... 1.7708-1.7716 (44.980-45.000)
Camshaft Bearing Shell Thickness, in (mm) ............... 0.0590-0.0594 (1.500-1.510)
Intake Cam Lobe Height, in (mm) ............... 1.4566-1.4606 (37.000-37.100)
Exhaust Cam Lobe Height, in (mm) ............... 1.4566-1.4606 (37.000-37.100)
Rocker Arm Shaft Outside Diameter, in (mm) ............... 0.5901-0.5905 (14.990-15.000)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.5913-0.5921 (15.020-15.040)
Rocker Arm Shaft-to-Bushing Clearance Play, in (mm) ............... 0.0007-0.0019 (0.020-0.050)
Tappet Lifter Body Outside Diameter, in (mm) ............... 0.4712-0.4720 (11.970-11.990)
Tappet Guide Bore Inside Diameter, in (mm) ............... 0.4724-0.4732 (12.000-12.020)
Tappet-to-Guide Clearance, in (mm) ............... 0.0003-0.0019 (0.010-0.050)
Idler Gear Shaft Outside Diameter, in (mm) ............... 1.3385-1.3391 (34.000-34.015)
Idler Gear Bushing Inside Diameter, in (mm) ............... 1.3397-1.3405 (34.030-34.050)
Idler Gear Shaft-to-Bushing Clearance, in (mm) ............... 0.0005-0.0019 (0.015-0.050)

Tightening Torques

Cylinder Head Bolt, lb-ft (Nm) ............... 54.2-57.8 (73.5-78.4)
Connecting Rod Cap Bolt, lb-ft (Nm) ............... 32.5-36.1 (44.1-49.0)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 65.1-72.3 (88.3-98.0)
Flywheel To Crankshaft Mount Bolt, lb-ft (Nm) ............... 57.8-65.1 (78.4-88.3)
Crankshaft Belt Drive Pulley Nut, lb-ft (Nm) ............... 86.8-101.2 (117.7-137.2)
Camshaft Thrust Gear Drive Nut, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Rocker Arm Shaft Support Nuts, lb-ft (Nm) ............... 21.7-25.3 (29.4-34.3)
Flywheel Housing Outer Cover Flange Bolt (M8), lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Flywheel Housing Outer Cover Flange Bolt (M10), lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Front Gear Case Timing Shield Bolt (M6), lb-ft (Nm) ............... 5.1-6.5 (6.9-8.8)
Front Gear Case Timing Shield Bolt (M8), lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Pan Sump Base Drain Plug, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Oil Pan Sealing Flange Mount Bolt (M6), lb-ft (Nm) ............... 5.1-6.5 (6.9-8.8)
Oil Pan Sealing Flange Mount Bolt (M8), lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Injection Pump Mount Body Flange Nut, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Injector Holder Double Flange Nuts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Injection Delivery Pipe Flare Nut, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Exhaust Manifold Flange Heat Nut, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Intake Manifold Stud Base Mount, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Water Pump Assembly Flange Support Studs, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Cooling Fan Pulley Nut, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Thermostart Heater Pre-heater Plug, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Glow Plug Secondary Grid, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Pressure Gauge Sensor Switch lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Water Temperature Gauge Thermal Switch, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Idler Gear Shaft Fixing Base Core Support Flange, lb-ft (Nm) ............... 21.7-25.3 (29.4-34.3)
Oil Pressure Regulator Relief Adjusting Plug, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Rocker Arm Adjusting Jam Screw, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Valve Cover Rocker Shield Dome Nut, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Fuel Feed Supply Pump Mounting Flange Stud, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Fuel Filter Housing Bracket Mount Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Filter Housing Adaptor Stud Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Alternator Pivot Mount Heavy Pivot Support Bolt, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Alternator Slotted Tension Adjuster Brace Lock Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Starter Motor Flange Mounting Bolt, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Crankcase Breather Valve Outer Plate Screws, lb-ft (Nm) ............... 3.6-5.1 (4.9-6.9)
Governor Housing Support End Cover Cap Bolt, lb-ft (Nm) ............... 5.1-6.5 (6.9-8.8)
Fuel Return Overflow Valve Cap Union Bolt, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Oil Delivery Main Gallery Hex End Grub Plugs, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Flywheel Housing Backing Plate Bolt, lb-ft (Nm) ............... 5.1-6.5 (6.9-8.8)
Crankshaft Rear Oil Seal Plate Housing Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Governor Weight Support Carrier Splined Drive Lock Nut, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Exhaust Manifold Deflector Heat Shield Screw, lb-ft (Nm) ............... 5.1-6.5 (6.9-8.8)
Air Intake Duct Preheater Adaptor Flange Fasteners, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)

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• Yanmar Engines Specs
  
• Yanmar 2TR13 Specs
  
• Yanmar 2TR13A Specs
  
• Yanmar 2TR15 Specs
  
• Yanmar 2TR16 Specs
  
• Yanmar 2TR17 Specs
  

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