Yanmar 2TR20A Specifications
| Engine Model: Yanmar 2TR20A |
| Engine Type: 4-stroke 2-cylinder naturally aspirated water-cooled diesel |
| Total Displacement: 69.9 cu.in (1.1 L) |
| Rated Engine Power: 20 Hp (14.9 kW) at 2400 rpm |
| Fuel System Type: Indirect injection |
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The Yanmar 2TR20A is a heavy-duty, 2-cylinder,
vertical, water-cooled diesel engine from Yanmar’s TR series, produced
from the mid-1970s through the 1990s. This engine was engineered
primarily for agricultural and industrial applications, gaining its
widest recognition as the powerplant for the Yanmar YM2000 compact
tractor. As an upgraded version of the 2TR20, the 2TR20A features a
larger 90 mm bore and 90 mm stroke, achieving a displacement of 1.10
liters and producing 20 hp at 2,400 rpm.
The engine utilizes an indirect injection (IDI) combustion system with a
swirl pre-combustion chamber - a design that provides smoother
operation, reduced combustion noise, and lower emissions compared to
direct injection engines of the same era. Built with a cast iron
cylinder block and overhead valve (OHV) configuration, the naturally
aspirated diesel is liquid-cooled and features a forced lubrication
system with a trochoid-type oil pump. The Yanmar 2TR20A became a
reference powerplant for compact utility tractors, demonstrating
exceptional longevity and reliability in agricultural service across
Asia, North America, and Europe.
Engine Code: 2TR20A
Engine Family: Yanmar TR series
Configuration: Inline 2-cylinder
Cycle: 4-cycle diesel
Valvetrain: Overhead Valve (OHV), 4 valves (2 per cylinder)
Displacement: 1.10 liters (1,100 cc; 69.9 cu.in)
Bore: 90.0 mm (3.54 in)
Stroke: 90.0 mm (3.54 in)
Compression Ratio: 20.0:1
Firing Order: 1-2
Aspiration: Naturally aspirated
Combustion System: Indirect injection (swirl pre-combustion chamber)
Fuel Injection Pressure: 157 bar (2,277 psi)
Maximum Power: 14.9-17.9 kW (20-24 hp) at 2400 rpm
Maximum Torque: 63.6 Nm (46.9 lb-ft) at 1800 rpm
Rated Speed: 2400 rpm
Torque Peak Speed: 1800 rpm
The cylinder block is constructed from cast iron, providing the
structural rigidity, vibration damping, and thermal mass required for
sustained agricultural diesel operation. The block features a vertical,
in-line 2-cylinder configuration with a deep-skirt design.
The cylinder bores are machined directly into the cast iron casting;
this engine does not use removable liners in its standard configuration.
The crankshaft is supported by three main bearings. The connecting rods
are forged steel. The pistons are aluminum alloy with a combustion bowl
designed to work with the indirect injection pre-combustion chamber
system.
The cylinder head is manufactured from cast iron, ensuring uniform
thermal expansion with the cylinder block and providing a robust sealing
surface for the head gasket under diesel compression pressures. The
valve arrangement is overhead valve (OHV) with two valves per cylinder -
one intake and one exhaust - actuated by pushrods from a camshaft
located within the cylinder block.
The valvetrain incorporates mechanical lash adjusters, requiring
periodic valve clearance inspection and manual adjustment. Valve
clearance (cold) is 0.20 mm (0.008 in) for both intake and exhaust
valves.
The distinctive feature of the cylinder head is the integrated swirl
pre-combustion chamber - a compact antechamber where fuel is partially
burned before entering the main combustion chamber. This indirect
injection system enables smoother engine operation and lower noise
levels compared to direct injection designs. The cylinder head
incorporates intake and exhaust passages and is drilled with dedicated
cooling channels around the valve seats and pre-combustion chamber.
The fuel system employs indirect injection with a mechanical in-line
injection pump. The pump is mounted to the side of the cylinder block
and is driven from the front gear train. The injection timing is set to
deliver fuel to the pre-combustion chamber. The injectors are
mechanical, spring-loaded pintle-type nozzles that open when fuel
pressure overcomes spring preload.
The injection pressure is specified at 157 bar (2,277 psi). A mechanical
centrifugal governor controls fuel delivery based on engine speed and
load demand. The system includes a fuel filter with a water separator
between the fuel tank and injection pump. A mechanical hand-priming
lever assists in bleeding air after filter changes.
The lubrication system is a pressurized, full-flow wet-sump design
utilizing a trochoid-type oil pump (a compact, positive-displacement
pump with inner and outer rotors). The oil pump is driven from the
crankshaft and draws fluid from a cast iron oil pan, with a total system
capacity of 4.5-5.0 liters (4.8-5.3 qt) including the filter.
A full-flow spin-on oil filter is mounted to the cylinder block.
Recommended oil viscosity is SAE 30 or 15W-40, conforming to API CC, CD,
or higher diesel specifications. Oil pressure specification at rated
speed is 30-50 psi (2.0-3.4 bar).
The cooling system is a pressure-controlled, thermostatically regulated
liquid-cooled arrangement with a belt-driven centrifugal water pump.
Coolant circulates through the cast iron cylinder block and cylinder
head. A wax-element thermostat, with an opening temperature of 71-77°C
(160-170°F), regulates coolant flow to the front-mounted radiator.
A 0.7-0.9 bar (10-13 psi) radiator cap maintains system pressure. A fan
mounted on the water pump pulley draws air through the radiator core.
The system uses an ethylene glycol-based diesel coolant.
| Intake and Exhaust Systems |
Intake System: The intake system includes a dry-type pleated paper air
filter with a restriction indicator, suitable for agricultural
environments. The intake manifold distributes air to the pre-combustion
chamber.
Exhaust System: The exhaust manifold is constructed from cast iron with
a single outlet flange.
Electrical System: The engine is equipped with a 12-volt starter motor
and a 35-ampere alternator. Glow plugs (one per cylinder) are installed
for cold-start assistance. The glow plug pre-heat system provides rapid
intake air heating for reliable starting in cold conditions.
Starting System: A key-operated starter switch engages the starter
motor. Glow plugs are pre-heated for 5-10 seconds before starting.
Governor System: The mechanical centrifugal governor within the
injection pump maintains engine speed under varying loads, calibrated
for agricultural equipment operation.
Valvetrain Drive: The camshaft is driven by a timing gear train from the
crankshaft - a durable arrangement eliminating belt or chain replacement
requirements.
Overall Length: 650 mm (25.6 in)
Overall Width: 500 mm (19.7 in)
Overall Height: 700 mm (27.6 in)
Dry Weight (engine only): 185-190 kg (408-419 lb)
Engine Oil Capacity (with filter change): 5.0 liters (5.3 qt)
Engine Oil Specification: SAE 30 or 15W-40, API CC, CD, CF-4, or higher
Oil Change Interval: 100 hours (severe duty) or 200 hours (normal duty)
Coolant Capacity (engine only): Approximately 3.5 liters (3.7 qt)
Coolant Specification: Ethylene glycol-based diesel coolant
Coolant Change Interval: 1,000 hours or 24 months
Thermostat Opening Temperature: 71-77°C (160-170°F)
Valve Clearance (cold, intake): 0.20 mm (0.008 in)
Valve Clearance (cold, exhaust): 0.20 mm (0.008 in)
Valve Clearance Adjustment Interval: 500 hours
Fuel Filter Replacement Interval: 400 hours
Air Filter Replacement Interval: Clean every 250 hours; replace as
required
Drive Belt Tension: Deflection of 10-12 mm (0.39-0.47 in) under 10 kg
(22 lb) force
Idle Speed (low, no load): 800-900 rpm
Rated Speed: 2400 rpm
Cylinder Head Bolts: 85-95 Nm (63-70 lb-ft)
Main Bearing Cap Bolts: 65-75 Nm (48-55 lb-ft)
Connecting Rod Cap Nuts: 40-45 Nm (30-33 lb-ft)
Crankshaft Pulley Bolt: 140-160 Nm (103-118 lb-ft)
Flywheel Bolts: 50-60 Nm (37-44 lb-ft)
Intake Manifold Bolts: 20-25 Nm (15-18 lb-ft)
Exhaust Manifold Nuts: 20-25 Nm (15-18 lb-ft)
Injector Hold-Down Clamp Screws: 20-25 Nm (15-18 lb-ft)
Glow Plugs: 15-20 Nm (11-15 lb-ft)
Rocker Arm Pedestal Bolts: 25-30 Nm (18-22 lb-ft)
Oil Pan Bolts: 10-15 Nm (7-11 lb-ft)
Water Pump Bolts: 20-25 Nm (15-18 lb-ft)
Oil Filter (spin-on): 15 Nm (11 lb-ft)
Starter Motor Mounting Bolts: 30-35 Nm (22-26 lb-ft)
Yanmar YM2000 Compact Tractor (1975-1985): The 2TR20A was the standard
engine for the YM2000, a compact utility tractor that became one of
Yanmar's most popular exports. The tractor produced 20 hp at 2,400 rpm
and was available in both 2WD and 4WD configurations. The engine is
durable and reliable, with proper maintenance enabling long-term
operation. The engine is paired with an 8-forward, 2-reverse gear
transmission and features a dry disc clutch.
Yanmar YM240 Compact Tractor (late 1970s-1980s): The 2TR20A powered the
YM240, a tractor nearly identical to the YM2000 but with different PTO
speed options and throttle control orientation. The engine produces 24
hp in this application, one of the higher ratings for the 2TR20A.
Yanmar YM195 Compact Tractor: The 2TR20A was installed in the YM195 as
part of the YM series range. This smaller chassis tractor utilized the
same engine platform as the YM2000 and YM240.
Yanmar YM1600 / YM1700 / YM1900 Tractors: The 2TR20A engine was
compatible with these mid-range Yanmar tractor models, sharing the same
engine mounting pattern and bellhousing configuration across the TR
series engine family.
Yanmar YB1200S Mini Excavator: The 2TR20A powered small construction
equipment including the YB1200S compact excavator. The engine's compact
dimensions and reliable starting characteristics suit construction
environments.
Industrial Machinery (Pumps, Generators, Compressors): The 2TR20A was
supplied as a power unit for industrial applications including
irrigation pumps, small generator sets, and air compressors. The engine
family compatibility extends across 2T84, 2T90, 2TR16, 2TR17, 2TR19, and
2TR20A variants.
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