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Hatz 1B20 Engine

The Hatz 1B20 is a compact, air-cooled, four-stroke, single-cylinder industrial diesel engine manufactured by Motorenfabrik Hatz. Positioned within the Hatz B-series, it features an upright cylinder configuration and is engineered primarily for robust, high-duty mobile and stationary industrial applications. The engine design incorporates a die-cast light alloy crankcase and a light alloy cylinder head to achieve a high power-to-weight ratio. It utilizes a direct injection combustion system, which yields optimized fuel-oriented mixture preparation and excellent exhaust gas quality, complying with strict emissions standards including EU Stage V and EPA/CARB parameters. The control cover houses the primary mechanical assemblies, including the governor, valve drive, injector pump drive, automatic mechanical decompression mechanism, and the oil pump.

The cylinder head utilizes an overhead valve configuration actuated via a traditional mechanical layout housed within the timing control cover. Valve clearance must be checked and adjusted strictly under ambient temperatures between 10C and 30C. Bore: 69 mm. Stroke: 65 mm. Total Displacement: 243 cc. Compression Ratio: 21:1 to 22:1. The engine relies on a forced-air cooling system. A mechanical cooling fan is incorporated directly into the flywheel assembly along with the AC generator. This unified flywheel design ensures the cooling air stream remains highly resistant to dust and particulate fouling. Cooling and combustion air is pulled directly through a dedicated intake opening on the blower housing side.

Fuel delivery relies on a mechanical direct injection architecture. The setup includes a fuel-oriented mixture preparation cycle feeding an injector nozzle driven directly from the control-cover gear train. Engine speed regulation is managed via a mechanical, spring-loaded governor providing a high degree of proportional accuracy. Combustion Air Filtration: Incoming air passes through an integrated dry-type air cleaner equipped with a replaceable paper cartridge and a built-in centrifugal pre-cleaner to separate coarse debris before the main filter element.

The engine uses a pressurized lubrication system driven by an internal oil pump located in the control cover. The circuit routes oil through a main-flow fine filter mesh to protect core bearings. Oil Pressure: 2.5 bars when operating at an oil temperature of 100C and an engine speed of 3000 rpm. Lubricant Specifications: Servicing requires oils conforming to ACEA B3/E4 or API CF/CH-4 classifications, utilizing SAE 5W-30 or 10W-30 viscosities. Oil drain plugs are positioned on both narrow sides of the crankcase to ease maintenance in tight installations.

General Technical Data

Engine Specifications

Engine Model ............... Hatz 1B20
Engine Type ............... 1-cylinder vertical air-cooled 4-stroke direct injection diesel
Number of Cylinders ............... 1
Engine Bore, in (mm) ............... 2.72 (69.0)
Engine Stroke, in (mm) ............... 2.56 (65.0)
Displacement, cu.in (cc) ............... 14.83 (243.0)
Rated Engine Power, hp (kW) ............... 4.70 (3.50) at 3600 rpm
Continuous Power Output, hp (kW) ............... 4.29 (3.20) at 3600 rpm
Rated Engine Speed, rpm ............... 1500-3600
Peak Torque ............... 7.74 lb-ft (10.50 Nm) at 2500 rpm
Idle Speed, rpm ............... 1000-1200
Aspiration Type ............... Naturally Aspirated
Operating Speed, rpm ............... 3000-3600
Compression Ratio ............... 22.0:1
Combustion System ............... Direct injection multi-orifice nozzle
Direction of Rotation ............... Anti-clockwise from power take-off side
Cylinder Block Material ............... Die-cast light alloy crankcase
Cylinder Head Type ............... Light alloy separate head
Lubrication System ............... Forced lubrication pressure circuit
Oil Pump Type ............... Gear-driven oil pump
Oil Filter Type ............... Screen type cleanable mesh filter mesh
Cooling System ............... Forced axial cooling air blower fan
Air Cleaner Type ............... Dry-type air cleaner cartridge integrated
Decompression System ............... Automatic mechanical decompression
Starting System ............... Recoil starter or electric option
Electrical System ............... 12V

Fuel System

Injection Pump Type ............... High pressure single plunger injection pump unit
Fuel Injection Nozzle ............... Multi-hole direct injection nozzle nozzle holder
Fuel Delivery Pressure, psi (bar) ............... 3625.94 (250.00)
Fuel Feed Method ............... Gravity feed from integrated tank top mounting
Fuel Filter Type ............... Disposable spin-on inline element cartridge filter
Standard Fuel Tank Capacity, gal (L) ............... 0.79 (3.00)
Optional Large Fuel Tank Capacity, gal (L) ............... 1.32 (5.00)
Approved Fuel Grades ............... EN 590, ASTM D 975 1D/2D, BS 2869 A1/A2
Fuel System Venting ............... Automatic venting via return line mechanism
Water Separator ............... Integrated fuel tank drain plug sediment bowl
Fuel Line Connection Diameter, in (mm) ............... 0.24 (6.00)
Injection Timing, degrees BTDC ............... 14.0-16.0 BTDC
Governing System ............... Mechanical centrifugal governor system spring-loaded
Stop Mechanism ............... Mechanical stop lever grounding circuit connection pin

Dimensions and Weight

Overall Length, in (mm) ............... 13.1 (330)
Overall Width, in (mm) ............... 15.6 (395)
Overall Height, in (mm) ............... 16.2 (410)
Dry Weight (Recoil Starter), lbs (kg) ............... 62 (28)
Dry Weight (Electric Starter), lbs (kg) ............... 75 (34)

Maintenance Data

Service Information

Oil Pressure at 3000 rpm, psi (bar) ............... 36.26 (2.50)
Oil Pressure at Idle Speed, psi (bar) ............... 8.70 (0.60)
Maximum Cylinder Head Temp, F (C) ............... 482.0 (250.0)
Maximum Oil Temperature, F (C) ............... 284.0 (140.0)
Inlet Valve Clearance (Cold), in (mm) ............... 0.008 (0.20)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.008 (0.20)

Engine Oil

Engine Oil Type .................. SAE 10W-40, SAE 10W-30, or 15W-40
API Service Classifications ......................... CF or CH-4
Engine Oil Capacity (Max Mark), qt (L) ............... 0.95 (0.90)
Engine Oil Capacity (Min Mark), qt (L) ............... 0.53 (0.50)

Service Intervals

Change engine oil ............... Every 250 hours
Clean oil filter ............... Every 1000 hours
Replace air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 500 hours
Valve clearance adjustment ............... Every 250 hours
Fuel system inspection ............... Every 250 hours
Check battery ............... Every 250 hours
Inspect breather valve ............... Every 1000 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 2.7165-2.7171 (69.000-69.015)
Cylinder Bore Wear Limit, in (mm) ............... 2.7205 (69.100)
Cylinder Out of Roundness, in (mm) ............... 0.0012 (0.030)
Cylinder Taper Maximum, in (mm) ............... 0.0016 (0.040)
Connecting Rod Big End Bore I.D, in (mm) ............... 1.6535-1.6541 (42.000-42.015)
Crankshaft Main Journal Diameter, in (mm) ............... 1.6531-1.6535 (41.980-41.990)
Crankpin Journal Diameter, in (mm) ............... 1.4957-1.4961 (37.990-38.000)
Crankshaft Main Bearing Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Crankshaft Big End Bearing Clearance, in (mm) ............... 0.0011-0.0026 (0.028-0.066)
Crankshaft Axial End Play, in (mm) ............... 0.0039-0.0118 (0.100-0.300)
Piston Skirt Outer Diameter, in (mm) ............... 2.7142-2.7148 (68.940-68.955)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.0018-0.0029 (0.045-0.075)
Piston Pin Outer Diameter, in (mm) ............... 0.8266-0.8268 (21.000-21.006)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.8272-0.8276 (21.012-21.022)
Piston Pin to Small End Bushing Clearance, in (mm) ............... 0.0002-0.0010 (0.006-0.026)
Top Ring Groove Height, in (mm) ............... 0.0787-0.0795 (2.000-2.020)
Second Ring Groove Height, in (mm) ............... 0.0787-0.0795 (2.000-2.020)
Oil Ring Groove Height, in (mm) ............... 0.1181-0.1189 (3.000-3.020)
Top Ring Side Clearance, in (mm) ............... 0.0016-0.0031 (0.040-0.080)
Second Ring Side Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Top Ring End Gap, in (mm) ............... 0.0079-0.0138 (0.200-0.350)
Second Ring End Gap, in (mm) ............... 0.0079-0.0138 (0.200-0.350)
Oil Ring End Gap, in (mm) ............... 0.0079-0.0138 (0.200-0.350)
Cylinder Head Flatness Distortion Max, in (mm) ............... 0.0020 (0.050)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2354-0.2358 (5.980-5.990)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2343-0.2346 (5.950-5.960)
Valve Guide Inside Diameter, in (mm) ............... 0.2362-0.2368 (6.000-6.015)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0004-0.0014 (0.010-0.035)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0016-0.0026 (0.040-0.065)
Valve Seat Angle, degrees ............... 45.0
Valve Face Angle, degrees ............... 45.0
Intake Valve Recess Depth, in (mm) ............... 0.0236-0.0354 (0.600-0.900)
Exhaust Valve Recess Depth, in (mm) ............... 0.0236-0.0354 (0.600-0.900)
Valve Spring Free Length, in (mm) ............... 1.4961 (38.000)
Camshaft Journal Diameter (Timing Side), in (mm) ............... 0.9445-0.9449 (24.000-24.010)
Camshaft Journal Diameter (Flywheel Side), in (mm) ............... 0.7874-0.7878 (20.000-20.010)
Camshaft Bearing Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Camshaft Axial End Play, in (mm) ............... 0.0020-0.0059 (0.050-0.150)
Tappet Bore Inside Diameter, in (mm) ............... 0.3937-0.3945 (10.000-10.022)
Tappet Stem Outer Diameter, in (mm) ............... 0.3921-0.3929 (9.960-9.980)

Tightening Torques

Cylinder Head Nut (1-Step), lb-ft (Nm) ............... 7.3 (10.0)
Cylinder Head Nut (2-Step), lb-ft (Nm) ............... 14.7 (20.0)
Cylinder Head Nut (3-Step), lb-ft (Nm) ............... 16.2 (22.0)
Connecting Rod Cap Bolt, lb-ft (Nm) ............... 23.6-25.8 (32.0-35.0)
Flywheel Mounting Center Hex Nut, lb-ft (Nm) ............... 59.0-66.3 (80.0-90.0)
Crankcase Cover Screws (M6), lb-ft (Nm) ............... 7.3-8.1 (10.0-11.0)
Crankcase Cover Screws (M8), lb-ft (Nm) ............... 16.9-18.4 (23.0-25.0)
Main Bearing Flange Cap Screws, lb-ft (Nm) ............... 16.9-18.4 (23.0-25.0)
Camshaft Thrust Washers Plate Screws, lb-ft (Nm) ............... 7.3-8.1 (10.0-11.0)
Rocker Arm Shaft Bracket Nut, lb-ft (Nm) ............... 16.9-18.4 (23.0-25.0)
Cylinder Head Cover Screw Cap, lb-ft (Nm) ............... 6.6-7.3 (9.0-10.0)
Fuel Pump Mounting Flange Hex Nuts, lb-ft (Nm) ............... 16.9-18.4 (23.0-25.0)
Fuel Valve Clamp Bracket Tension Nut, lb-ft (Nm) ............... 11.0-12.5 (15.0-17.0)
High Pressure Fuel Delivery Line Nuts, lb-ft (Nm) ............... 18.4-22.1 (25.0-30.0)
Fuel Injection Nozzle Holder Cap, lb-ft (Nm) ............... 29.5-33.2 (40.0-45.0)
Oil Drain Hex Plug, lb-ft (Nm) ............... 36.9 (50.0)
Oil Pressure Switch, lb-ft (Nm) ............... 11.1-14.7 (15.0-20.0)
Oil Pump Assembly Plate Screws, lb-ft (Nm) ............... 5.2-6.6 (7.0-9.0)
Governor Weight Carrier Assembly Nut, lb-ft (Nm) ............... 25.8-29.5 (35.0-40.0)
Speed Control Lever Pivot Nut, lb-ft (Nm) ............... 8.8-11.1 (12.0-15.0)
Recoil Starter Assembly Housing Screws, lb-ft (Nm) ............... 5.1-6.6 (7.0-9.0)
Electric Starter Flange Mounting Nuts, lb-ft (Nm) ............... 33.2-36.9 (45.0-50.0)
Alternator Mounting Screws Internal Block, lb-ft (Nm) ............... 5.1-6.6 (7.0-9.0)
Exhaust Silencer Muffler Flange Nuts, lb-ft (Nm) ............... 16.9-18.4 (23.0-25.0)
Exhaust Heat Shield Mounting Bolts, lb-ft (Nm) ............... 5.1-6.6 (7.0-9.0)
Dry Air Filter Housing Mount Bracket Nut, lb-ft (Nm) ............... 7.4-8.1 (10.0-11.0)
Air Filter Element Center Fastener, lb-ft (Nm) ............... 1.4-2.2 (2.0-3.0)
Fuel Tank Base Cradle Mounting Nuts, lb-ft (Nm) ............... 11.1-13.3 (15.0-18.0)
Fuel Tank Bottom Drain Plug, lb-ft (Nm) ............... 14.7-18.4 (20.0-25.0)
Decompression Engagement Pivot Pin, lb-ft (Nm) ............... 11.1-13.3 (15.0-18.0)
Breather Valve Cover Plate Screws, lb-ft (Nm) ............... 2.9-3.7 (4.0-5.0)
Crankcase Breather Assembly Screw, lb-ft (Nm) ............... 3.7-4.4 (5.0-6.0)
Crankshaft PTO Side Oil Seal Carrier Screws, lb-ft (Nm) ............... 7.4-8.1 (10.0-11.0)
Timing Gear Cover Hole Cap Plug, lb-ft (Nm) ............... 18.4-22.1 (25.0-30.0)
Governor Speed Stop Adjustment Screw, lb-ft (Nm) ............... 5.2-5.9 (7.0-8.0)

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• Hatz Engines Specs
  
• Hatz 1B20-6 Specs
  
• Hatz 1B30 Specs
  
• Hatz 1B30E Specs
  
• Hatz 1B40 Specs
  
• Hatz 1B50 Specs
  
• Hatz 1B50E Specs
  

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