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Yanmar 2T80 Engine

The Yanmar 2T80 is a compact, vertical, 2-cylinder, 4-cycle inline diesel engine primarily designed for compact agricultural equipment, most notably powering vintage utility tractors like the John Deere 650. Built with a heavy-duty cast-iron cylinder block, it is recognized for its thermal efficiency, high torque output at low operating speeds, and long-term mechanical durability under sustained load conditions.

The cylinder head utilizes an overhead valve design featuring two valves per cylinder (one intake, one exhaust) actuated by pushrods and rocker arms driven by a gear-train camshaft inside the block. A decompression system mechanism is integrated into the rocker arm assembly to facilitate manual rotation during service or cold-weather starting procedures. The internal cylinder geometry features a cross-flow combustion configuration. The internal dimensions consist of a bore of 80 mm (3.15 inches) and a stroke of 85 mm (3.35 inches). Total engine displacement measures 52.1 cubic inches (0.9 Liters).

Engine lubrication is managed through a fully forced, pressure-fed system driven by a internal trochoid-type oil pump. The oil pump draws lubricant through an internal oil strainer in the oil pan and routes it directly through a full-flow replaceable spin-on oil filter. Main galleries feed pressurized oil straight to the crankshaft main bearings, connecting rod journals, and up to the overhead rocker assembly. Thermal regulation is achieved via a closed-loop, forced liquid-cooling design. A belt-driven centrifugal water pump circulates coolant through the cylinder block water jackets and cylinder head passages. System temperature is mechanically regulated by a pellet-type thermostat to maintain stable combustion temperatures.

Fuel distribution relies on a highly precise mechanical injection setup. Fuel is drawn from the storage tank by a mechanical fuel feed pump and passes through a primary water separator and fuel filter assembly. Clean diesel fuel is supplied to a deck-mounted, individual-cylinder Bosch-type inline fuel injection pump assembly. The high-pressure injection pump times and meters fuel delivery through steel lines to individual fuel injection valves that spray directly into the pre-combustion chamber zones. To assist with cold-weather starting procedures, the system is backed by an electrical "Thermostart" air preheating intake grid plug.

General Technical Data

Engine Specifications

Engine Model ............... Yanmar 2T80
Engine Type ............... 4-cycle vertical inline 2-cylinder liquid-cooled diesel
Number of Cylinders ............... 2
Cylinder Arrangement ............... In-line vertical
Engine Bore, in (mm) ............... 3.15 (80.0)
Engine Stroke, in (mm) ............... 3.35 (85.0)
Displacement, cu.in (L) ............... 52.1 (0.854)
Gross Power, hp (kW) ............... 17.0 (12.7)
Net Power, hp (kW) ............... 15.0 (11.2)
Rated Speed, rpm ............... 2600
Max No-Load Speed, rpm ............... 2800
Low Idle Speed, rpm ............... 800-900
Peak Torque, lb-ft (Nm) ............... 36.8 (50.0) at 1900 rpm
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 22.5:1
Firing Order ............... 1-2
Direction of Rotation ............... Counter-clockwise viewed from flywheel side
Cylinder Block Type ............... Monoblock cast iron
Cylinder Head Type ............... One-piece cast iron crossflow
Combustion Chamber ............... Swirl pre-combustion chamber swirl type
Valves per Cylinder ............... 2 (1 intake, 1 exhaust)
Valve Arrangement ............... Overhead valve (OHV)
Camshaft Drive Type ............... Gear-driven train
Lubrication System ............... Full-pressure feed
Oil Pump Type ............... Trochoid rotor type gear-driven
Oil Filter Type ............... Full-flow spin-on cartridge
Cooling System ............... Forced liquid circulation
Water Pump Type ............... Belt-driven centrifugal pump
Cooling Fan Type ............... Suction or pusher 4-blade plastic
Air Cleaner Type ............... Dry dual-element or cyclone type
Pre-heating Starting Aid ............... Thermostart glow plug system
Starting System ............... Electric starter motor
Electrical System, V ............... 12
Alternator Capacity, A ............... 15 or 35
Starter Motor Power, hp (kW) ............... 1.34 (1.0)

Fuel System

Fuel Injection Pump Type ............... Yanmar inline Bosch-type Monoblock YPD
Fuel Injection Pump Drive ............... Camshaft gear-driven
Fuel Injector Nozzle Type ............... Throttle nozzle type
Fuel Injector Opening Pressure, psi (bar) ............... 1991-2132 (137.3-147.1)
Fuel Injection Timing, deg BTDC ............... 18-20
Fuel Transfer Pump Type ............... Mechanical diaphragm type
Governor Type ............... Mechanical centrifugal all-speed type
Fuel Filter Type ............... Spin-on cartridge with water separator
Fuel Feed Line Diameter, in (mm) ............... 0.236 (6.0)
Fuel Return Line Diameter, in (mm) ............... 0.157 (4.0)
Fuel Tank Recommended Capacity, gal (L) ............... 5.8 (22.0)
Recommended Fuel Grade ............... Diesel No. 2-D or Ultra Low Sulfur Diesel
Maximum Fuel Pump Suction Lift, ft (m) ............... 3.3 (1.0)
Maximum Fuel Return Line Backpressure, psi (bar) ............... 2.9 (0.2)
Fuel Injector Spray Angle, deg ............... 4
Plunger Diameter, in (mm) ............... 0.236 (6.0)
Plunger Stroke, in (mm) ............... 0.275 (7.0)
Delivery Valve Opening Pressure, psi (bar) ............... 426 (29.4)
Fuel System Priming Method ............... Manual priming lever on feed pump
Fuel Leak-off Configuration ............... External rail return to fuel tank
Injection Nozzle Hole Diameter, in (mm) ............... 0.039 (1.0)

Dimensions and Weight

Overall Length, in (mm) ............... 17.5 (445)
Overall Width, in (mm) ............... 16.2 (410)
Overall Height, in (mm) ............... 21.8 (555)
Dry Weight, lbs (kg) ............... 200 (91)
Wet Weight, lbs (kg) ............... 216 (98)

Maintenance Data

Service Information

Standard Compression Pressure, psi (bar) ............... 500 (34.1)
Minimum Compression Pressure, psi (bar) ............... 400 (27.5)
Oil Standard at Rated Speed, psi (bar) ............... 42.7-56.9 (2.9-3.9)
Oil Standard at Idle Speed, psi (bar) ............... 14.2 (1.0)
Maximum Lubricating Oil Temperature, F (C) ............... 230 (110.0)
Thermostat Valve Opening Temperature, F (C) ............... 160 (71.1)
Thermostat Valve Full Open Temperature, F (C) ............... 185 (85.0)
Radiator Cap Pressure Rating, psi (bar) ............... 12.8 (0.9)
Fan Belt Tension Deflection, in (mm) ............... 0.394-0.591 (10.0-15.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.008 (0.203)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.008 (0.203)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, SAE 10W-30, or 5W-20
API Service Classifications ......................... CD, CE, CF, or CF-4
Engine Oil Capacity, Oil Pan, qts (L) ............... 2.1 (2.0)
Engine Oil Capacity with Filter, qts (L) ............... 2.5 (2.4)
Cooling System Capacity, qts (L) ............... 1.6 (1.5)
Cooling Capacity with Radiator, qts (L) ............... 4.0 (3.8)

Service Intervals

Change oil and filter ............... Every 100 hours
Inspect air cleaner ............... Every 50 hours
Replace air cleaner ............... Every 250 hours
Replace fuel filter ............... Every 250 hours
Valve clearance adjustment ............... Every 300 hours
Fuel system inspection ............... Every 500 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) ............... 3.149-3.151 (80.000-80.030)
Cylinder Bore Out-of-Roundness, in (mm) ............... 0.0004 (0.01)
Cylinder Bore Taper, in (mm) ............... 0.0004 (0.01)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.985-0.986 (25.020-25.040)
Connecting Rod Big End Journal Diameter, in (mm) ............... 1.771-1.772 (45.000-45.015)
Connecting Rod Bearing Internal Diameter, in (mm) ............... 1.773-1.774 (45.035-45.060)
Connecting Rod Bearing Oil Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Connecting Rod Big End Side Play, in (mm) ............... 0.0039-0.0118 (0.100-0.300)
Crankshaft Main Journal Outer Diameter, in (mm) ............... 1.968-1.969 (50.000-50.015)
Main Bearing Shell Internal Diameter, in (mm) ............... 1.970-1.971 (50.035-50.065)
Main Bearing Oil Clearance, in (mm) ............... 0.0008-0.0026 (0.020-0.065)
Crankshaft End Play, in (mm) ............... 0.0043-0.0083 (0.110-0.210)
Piston Skirt Diameter, in (mm) ............... 3.146-3.147 (79.910-79.940)
Piston to Cylinder Wall Clearance, in (mm) ............... 0.0024-0.0035 (0.060-0.090)
Piston Pin Bore Outer Diameter, in (mm) ............... 0.984-0.985 (25.000-25.010)
Piston Pin Outside Diameter, in (mm) ............... 0.983-0.984 (24.990-25.000)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0000-0.0008 (0.000-0.020)
Piston Pin to Small End Bushing Clearance, in (mm) ............... 0.0008-0.0020 (0.020-0.050)
Top Ring Groove Width, in (mm) ............... 0.079-0.080 (2.020-2.040)
Second Ring Groove Width, in (mm) ............... 0.079-0.080 (2.020-2.040)
Oil Ring Groove Width, in (mm) ............... 0.158-0.159 (4.010-4.030)
Top Ring Side Clearance, in (mm) ............... 0.0024-0.0037 (0.060-0.095)
Second Ring Side Clearance, in (mm) ............... 0.0020-0.0033 (0.050-0.085)
Oil Ring Side Clearance, in (mm) ............... 0.0012-0.0026 (0.030-0.065)
Top Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Second Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Oil Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Cylinder Head Deck Flatness Distortion, in (mm) ............... 0.0012 (0.030)
Cylinder Block Upper Top Deck Flatness, in (mm) ............... 0.0012 (0.030)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.273-0.274 (6.955-6.970)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.272-0.273 (6.940-6.955)
Intake Valve Guide Internal Diameter, in (mm) ............... 0.275-0.276 (7.000-7.015)
Exhaust Valve Guide Internal Diameter, in (mm) ............... 0.275-0.276 (7.000-7.015)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0012-0.0024 (0.030-0.060)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0018-0.0030 (0.045-0.075)
Intake Valve Seat Angle, deg ............... 45
Exhaust Valve Seat Angle, deg ............... 45
Intake Valve Margin Thickness, in (mm) ............... 0.039 (1.000)
Exhaust Valve Margin Thickness, in (mm) ............... 0.039 (1.000)
Valve Spring Free Length, in (mm) ............... 1.457 (37.000)
Camshaft Main Journal Diameter (Front), in (mm) ............... 1.574-1.575 (40.000-40.025)
Camshaft Main Journal Diameter (Middle), in (mm) ............... 1.574-1.575 (40.000-40.025)
Camshaft Main Journal Diameter (Rear), in (mm) ............... 1.574-1.575 (40.000-40.025)
Camshaft Bearing Bore Internal Diameter, in (mm) ............... 1.576-1.578 (44.050-44.085)
Camshaft Journal Oil Clearance, in (mm) ............... 0.0010-0.0033 (0.025-0.085)
Intake Cam Lobe Height, in (mm) ............... 1.335-1.339 (33.900-34.000)
Exhaust Cam Lobe Height, in (mm) ............... 1.335-1.339 (33.900-34.000)
Camshaft End Play, in (mm) ............... 0.0020-0.0059 (0.050-0.150)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.550-0.551 (13.960-13.980)
Rocker Arm Bushing Internal Bore Diameter, in (mm) ............... 0.551-0.552 (14.000-14.020)
Rocker Arm Bushing to Shaft Clearance Production, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Tappet Pushrod Guide Bore Internal Diameter, in (mm) ............... 0.472-0.473 (12.000-12.018)
Tappet Lifter Body Outside Diameter, in (mm) ............... 0.470-0.471 (11.960-11.980)
Tappet to Block Guide Bore Clearance, in (mm) ............... 0.0008-0.0023 (0.020-0.058)
Idler Gear Shaft Outside Diameter, in (mm) ............... 1.376-1.377 (34.950-34.975)
Idler Gear Bushing Internal Bore Diameter, in (mm) ............... 1.378-1.379 (35.000-35.025)
Idler Gear Shaft to Bushing Clearance, in (mm) ............... 0.0010-0.0030 (0.025-0.075)

Tightening Torques

Cylinder Head Bolts (Step 1), lb-ft (Nm) ............... 22.0 (30.0)
Cylinder Head Bolts (Step 2), lb-ft (Nm) ............... 44.0 (60.0)
Cylinder Head Bolts (Step 3), lb-ft (Nm) ............... 54.2-57.8 (73.5-78.5)
Connecting Rod Cap Bolts, lb-ft (Nm) ............... 23.1-26.0 (31.4-35.3)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 39.8-43.4 (54.0-58.8)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 39.8-43.4 (54.0-58.8)
Flywheel Fastener Mounting Bolts, lb-ft (Nm) ............... 43.4-47.0 (58.8-63.7)
Crankshaft Pulley End Center Bolt, lb-ft (Nm) ............... 61.4-68.7 (83.3-93.1)
Camshaft Gear Thrust Plate Lock Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Rocker Arm Shaft Support Bracket Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Rocker Arm Adjusting Screw Jam Locknuts, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Valve Cover Bonnet Retaining Nuts, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Timing Gear Case Cover Bolts (M6), lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Timing Gear Case Cover Bolts (M8), lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Pan Oil Sump Drain Plug Screw, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Oil Pan Body Housing Flange Bolts, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Oil Pump Internal Plate Cover Screws, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Idler Gear Shaft Support Retention Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Fuel Injection Pump Retaining Nuts Flange, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Fuel Injection Pump Drive Gear Nut, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Fuel Injector Assembly Fixing Nuts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Fuel Injector Retaining Bracket Clamp Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Fuel High Pressure Line Union Delivery Nuts, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Injection Pump Delivery Valve Holder, lb-ft (Nm) ............... 25.3-28.9 (34.3-39.2)
Fuel Leak-Off Return Rail Banjo Connector Bolt, lb-ft (Nm) ............... 5.8-7.2 (7.8-9.8)
Fuel Filter Bracket Structural Mounting Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Water Pump Assembly Flange Mounting Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Cooling Fan Pulley Retaining Bolts, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Thermostat Housing Cover Retaining Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Coolant Temperature Sensor Sender Unit Switch, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Pressure Switch Sensor Unit, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Intake Manifold Flange Fastener Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Exhaust Manifold Stud Flange Fastener Nuts, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Starter Motor Structural Flange Mounting Bolts, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Alternator Pivot Long Mounting Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Alternator Adjusting Tension Bracket Brace Bolt, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Glow Plug Structural Threaded Installation Body, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Glow Plug Wiring Harness Small Electrical Nut, lb-ft (Nm) ............... 1.1-1.4 (1.5-2.0)
Flywheel Housing Plate Adapter Mounting Bolts, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Crankcase Breather Assembly Retention Screws, lb-ft (Nm) ............... 3.6-5.1 (4.9-6.9)

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