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Wisconsin AB Engine

The Wisconsin Model AB is a heavy-duty, single-cylinder, four-cycle, air-cooled industrial engine. Designed for high-torque, continuous-duty applications, this engine utilizes a cast-iron block and an integrated design capable of operating under demanding field conditions. The four-stroke operational cycle means each of the four separate procedures (suction, compression, expansion, and exhaust) requires a single complete stroke of the piston, resulting in one power stroke for every two revolutions of the crankshaft. The structural build emphasizes heavy-duty component design, including a forged steel crankshaft, a robust governor assembly, and an easily serviceable top end, making it a reliable power plant for vintage agricultural and industrial machinery.

The engine features a side-valve (L-head) configuration built directly into the cylinder block. Both the intake and exhaust valves operate vertically, driven by a camshaft located in the crankcase. The heat-resistant alloy steel exhaust valves ensure durability under high operating temperatures. Valve clearance must be adjusted at the tappets when the engine is cold, in accordance with standard workshop tolerance specifications. Bore: 2.50 inches (63.5 mm). Stroke: 2.75 inches (69.85 mm). Total Displacement: 13.5 cubic inches (221 cc).

The fuel delivery architecture consists of a gravity-fed or pump-assisted system drawing from a 1-gallon fuel tank. Liquid fuel passes through a glass sediment bowl/strainer assembly designed to capture water and particulate matter before entering the carburetor inlet. A balanced, side-draft or up-draft Tillotson or Zenith carburetor manages air-fuel mixing, maintaining precise ratios across the entire operational load range. The air intake is protected by an oil-bath style air cleaner containing 0.5 pints of engine oil to capture airborne contaminants. Final engine speed regulation is maintained by a mechanical, centrifugal flyball governor linked directly to the carburetor throttle shaft to compensate for varying loads.

Lubrication is managed via a constant-level splash system. An internal, mechanically driven plunger pump actively maintains a proper oil level inside a specialized trough positioned directly beneath the connecting rod. As the connecting rod dipper strikes the fluid in the trough, it creates an oil mist that lubricates internal bearings, the camshaft, and the cylinder wall. The internal crankcase fluid capacity is 1.25 pints (0.6 liters). Technicians must change the oil every 50 hours of operation under normal conditions, using SAE 30 weight oil for typical operational temperatures spanning 40F to 120F.

Cooling is accomplished via a forced-air circulation method. A combination fan-flywheel draws air in and pushes it through a structured system of metal ducts and baffle plates inside a sheet metal blower shroud. This shroud systematically directs air across the cooling fins of the cast-iron cylinder block and cylinder head to ensure uniform heat dissipation. Operating the engine with any portion of this sheet metal shrouding removed will instantly compromise cooling efficiency and cause thermal damage.

General Technical Data

Engine Specifications

Engine Model ............... Wisconsin AB
Engine Type ............... 4-cycle single-cylinder L-head air-cooled gasoline
Number of Cylinders ............... 1
Cylinder Arrangement ............... Vertical upright single-cylinder
Engine Bore, in (mm) ............... 2.50 (63.50)
Engine Stroke, in (mm) ............... 2.75 (69.85)
Displacement, cu.in (cc) ............... 13.50 (221.22)
Rated Power at 1600 rpm, hp (kW) ............... 1.70 (1.27)
Rated Power at 1800 rpm, hp (kW) ............... 2.00 (1.49)
Rated Power at 2200 rpm, hp (kW) ............... 2.50 (1.86)
Rated Power at 2600 rpm, hp (kW) ............... 3.00 (2.24)
Maximum Power, hp (kW) ............... 3.20 (2.39) at 2600 rpm
Rated Speed, rpm ............... 1600-2600
Peak Torque, lb-ft (Nm) ............... 6.50 (8.81) at 1600 rpm
Idle Speed, rpm ............... 500-600
Cooling System ............... Air-cooled via flywheel blower shroud fan
Compression Ratio ............... 5.1:1
Rotation Direction ............... Counter-clockwise facing power take-off shaft
Muffler Type ............... Direct threaded exhaust type
Crankshaft Type ............... Counterbalanced forged steel alloy
Valve Location ............... Side valve L-head setup in cylinder block
Camshaft Type ............... Forged steel integral lobes gear driven
Cylinder Block Material ............... Heavy duty cast iron
Cylinder Head Material ............... Cast iron removable type
Crankcase Material ............... Cast iron integral with block
Piston Material ............... Aluminum alloy split-skirt cam-ground
Connecting Rod Material ............... Forged steel split journal
Main Bearings Type ............... Tapered roller bearings on both ends
Lubrication System ............... Constant-level splash lubrication
Oil Pump Type ............... Plunger type circulating pump
Air Cleaner Type ............... Oil bath type cleaner
Starting System ............... Rope start with starter pulley wrap sheave
Ignition System ............... High tension magneto drive gear system
Magneto Model ............... Fairbanks Morse or Wico base mounted
Spark Plug Type ............... Champion No. 16 or AC No. C86 Commercial

Fuel System

Carburetor Model ............... Stromberg UR-3 or UR-4 updraft type
Carburetor Alternative Model ............... Zenith 161 series or Tillotson side draft
Fuel Tank Capacity, gal (L) ............... 1.00 (3.785)
Fuel Grade Minimum Octane Rating ............... 74 octane regular gasoline
Recommended Fuel Type ............... Clean leaded or unleaded automotive gasoline
Fuel Feed Type ............... Gravity flow from tank to carburetor
Fuel Strainer Type ............... Sediment glass bowl with screen mesh filter
Fuel Line Material ............... Copper tubing with brass inverted flare nuts
Fuel Line Diameter, in (mm) ............... 0.25 (6.35)
Carburetor Inlet Thread Size, in ............... 0.125 NPT thread
Carburetor Drip Elbow Fitting, in ............... 0.125 street elbow fitting
High Speed Needle Valve Initial Setting ............... 3 full turns open from seat
High Speed Needle Adjustment Under Load ............... 1.625 turns off seat variable
Idle Mixture Needle Initial Setting ............... 3 full turns open from seated seat
Float Level Distance Setting, in (mm) ............... 0.687 (17.46)
Float Parallel Alignment Standard ............... Edges parallel with bowl gasket face
Choke Valve Control ............... Manual lever with optional remote wire hookup
Throttle Valve Operation ............... Controlled by centrifugal flyball governor rod
Governor Type ............... Flyball mechanical centrifugal type running in oil
Governor Location ............... Internal cam gear assembly
Governor Control Spring Type ............... Variable speed governor tension spring
Governor Control Lever Part Number ............... VE-363-A assembly
Carburetor Gasket Thickness, in (mm) ............... 0.031 (0.79)
Air Horn Diameter, in (mm) ............... 1.125 (28.57)
Venturi Diameter Size, in (mm) ............... 0.562 (14.28)
Fuel Shutoff Valve Type ............... Manual needle shutoff handle integrated in strainer

Dimensions and Weight

Overall Engine Height, in (mm) ............... 19.5 (495)
Overall Engine Width, in (mm) ............... 14.8 (375)
Overall Engine Length, in (mm) ............... 15.2 (385)
Dry Weight, lbs (kg) ............... 76 (34.5)
Shipping Weight, lbs (kg) ............... 95 (43.0)

Maintenance Data

Service Information

Compression Pressure Range, psi (bar) ............... 75-90 (5.17-6.20)
Spark Plug Gap, in (mm) ............... 0.030 (0.762)
Breaker Point Gap, in (mm) ............... 0.015 (0.381)
Timing Advance Angle ............... 20 degrees BTDC
Intake Valve Clearance (Cold), in (mm) ............... 0.008 (0.203)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.008 (0.203)

Engine Oil

Engine Oil Type .................. SAE 30, SAE 20W, or SAE 10W
API Service Classifications ......................... SE, SF, SG, or CC
Crankcase Oil Capacity, pints (L) ............... 1.25 (0.59)
Air Cleaner Reservoir Capacity, pints (L) ............... 0.50 (0.24)
Reduction Gear Housing Capacity, pints (L) ............... 0.50 (0.24)
Clutch Housing Assembly Capacity, pints (L) ............... 0.50 (0.24)

Service Intervals

Change engine oil ............... Every 50 hours
Inspect air cleaner ............... Every 8 hours
Service air cleaner ............... Every 50 hours
Clean fuel strainer ............... Every 50 hours
Valve clearance adjustment ............... Every 150 hours
Fuel system inspection ............... Every 100 hours
Clean spark plug ............... Every 100 hours
Replace spark plug ............... Every 300 hours
Clean cooling fin ............... Every 8 hours
Flush/Clean fuel tank ............... Every 500 hours
Change reduction gear oil ............... Every 500 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 2.5000-2.5005 (63.500-63.512)
Cylinder Bore Taper Maximum, in (mm) ............... 0.0015 (0.038)
Cylinder Bore Out of Roundness, in (mm) ............... 0.0010 (0.025)
Cylinder Wall Total Thickness, in (mm) ............... 0.375 (9.52)
Crankshaft End Play, in (mm) ............... 0.002-0.004 (0.051-0.101)
Crankpin Journal Diameter, in (mm) ............... 1.3750-1.3755 (34.925-34.937)
Connecting Rod Radial Clearance, in (mm) ............... 0.0008-0.0020 (0.020-0.050)
Connecting Rod Side Clearance, in (mm) ............... 0.004-0.008 (0.101-0.203)
Connecting Rod Length Center to Center, in (mm) ............... 5.00 (127.00)
Connecting Rod Big End Bore Diameter, in (mm) ............... 1.3760-1.3765 (34.950-34.963)
Piston Skirt Outside Diameter, in (mm) ............... 2.4960-2.4965 (63.398-63.411)
Piston to Cylinder Wall Clearance, in (mm) ............... 0.0035-0.0045 (0.088-0.114)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.6250-0.6253 (15.875-15.882)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0001-0.0005 (0.0025-0.0127)
Piston Pin to Con Rod Bushing Clearance, in (mm) ............... 0.0003-0.0007 (0.0076-0.0177)
Top Ring Grove Width, in (mm) ............... 0.093 (2.38)
Second Ring Grove Width, in (mm) ............... 0.093 (2.38)
Oil Ring Grove Width, in (mm) ............... 0.1875 (4.76)
Top Ring Groove Side Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.088)
Second Ring Groove Side Clearance, in (mm) ............... 0.0015-0.0030 (0.038-0.076)
Oil Ring Groove Side Clearance, in (mm) ............... 0.0015-0.0030 (0.038-0.076)
Top Ring End Gap, in (mm) ............... 0.007-0.015 (0.177-0.381)
Cylinder Head Flatness Distortion Maximum, in (mm) ............... 0.0030 (0.076)
Cylinder Block Deck Flatness Distortion, in (mm) ............... 0.0030 (0.076)
Intake Valve Head Diameter, in (mm) ............... 1.187 (30.16)
Exhaust Valve Head Diameter, in (mm) ............... 1.187 (30.16)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.3105-0.3110 (7.886-7.899)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.3095-0.3100 (7.861-7.874)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0015-0.0030 (0.038-0.076)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0025-0.0040 (0.063-0.101)
Valve Seat Angle, Degree ............... 45
Valve Face Angle, Degree ............... 44.5
Valve Guide Inside Diameter, in (mm) ............... 0.3125-0.3135 (7.937-7.962)
Valve Seat Contact Width, in (mm) ............... 0.125-0.156 (3.175-3.96
Valve Head Margin Thickness, in (mm) ............... 0.0625 (1.587) after refacing cut
Valve Spring Free Length, in (mm) ............... 1.750 (44.45)
Camshaft Journal Diameter (Front), in (mm) ............... 0.8750-0.8755 (22.225-22.237)
Camshaft Journal Diameter (Rear), in (mm) ............... 0.7500-0.7505 (19.050-19.062)
Camshaft Radial Clearance, in (mm) ............... 0.0015-0.0030 (0.038-0.076)
Camshaft Running Clearance, in (mm) ............... 0.0050 (0.127)
Camshaft End Play, in (mm) ............... 0.002-0.006 (0.050-0.152)
Cam Lobe Height (Intake), in (mm) ............... 1.255-1.260 (31.877-32.004)
Cam Lobe Height (Exhaust), in (mm) ............... 1.255-1.260 (31.877-32.004)
Tappet Guide Bore Block Inside Diameter, in (mm) ............... 0.4375-0.4385 (11.112-11.137)
Tappet Stem Outside Diameter, in (mm) ............... 0.4350-0.4360 (11.049-11.074)
Tappet Stem Running Clearance, in (mm) ............... 0.0045 (0.114)

Tightening Torques

Cylinder Head Mounting Screws, lb-ft (Nm) ............... 14.0-18.0 (18.9-24.4)
Connecting Rod Bolt Hex Nut, lb-ft (Nm) ............... 16.0-20.0 (21.6-27.1)
Spark Plug Assembly, lb-ft (Nm) ............... 25.0-30.0 (33.9-40.6)
Flywheel Retaining Nut, lb-ft (Nm) ............... 50.0-60.0 (67.7-81.3)
Crankcase Base Plate Screw, lb-ft (Nm) ............... 6.0-8.0 (8.1-10.8)
Cylinder Block to Crankcase Base Cap Screw, lb-ft (Nm) ............... 32.0-36.0 (43.3-48.8)
Magneto Housing Base Mounting Bolts, lb-ft (Nm) ............... 18.0-22.0 (24.4-29.8)
Carburetor to Intake Flange Mounting Nut, lb-ft (Nm) ............... 8.0-12.0 (10.8-16.2)
Intake Exhaust Manifold Bolt, lb-ft (Nm) ............... 14.0-18.0 (18.9-24.4)
Crankcase Oil Pan Drain Pipe Plug, lb-ft (Nm) ............... 15.0-20.0 (20.3-27.1)
Governor Lever Clamp Bolt Adjustment Nut, lb-ft (Nm) ............... 4.0-6.0 (5.4-8.1)
Air Shroud and Blower Housing Screw, lb-ft (Nm) ............... 3.5-5.0 (4.7-6.7)
Fuel Tank Bracket to Cylinder Head Screw, lb-ft (Nm) ............... 14.0-18.0 (18.9-24.4)
Gear Cover Plate Fasteners-Block, lb-ft (Nm) ............... 10.0-14.0 (13.5-18.9)
Valve Inspection Cover Center Nut, lb-ft (Nm) ............... 3.0-5.0 (4.0-6.7)
Reduction Gear Case Outer Housing Bolt, lb-ft (Nm) ............... 18.0-22.0 (24.4-29.8)
Clutch Back Plate Mounting Socket Screw, lb-ft (Nm) ............... 22.0-26.0 (29.8-35.2)
Muffler Locking Nut Threaded Exhaust Pipe, lb-ft (Nm) ............... 25.0-35.0 (33.9-47.4)
Breaker Point Locking Retainer Screw, lb-in (Nm) ............... 15.0-20.0 (1.69-2.25)
Magneto Coil Core Clamp Fixing Fastener, lb-in (Nm) ............... 25.0-30.0 (2.82-3.38)
Fuel Strainer Bracket Assembly Screw, lb-ft (Nm) ............... 6.0-9.0 (8.1-12.2)
Air Cleaner Clamping Band Bolt Assembly, lb-in (Nm) ............... 20.0-30.0 (2.25-3.38)
Starting Pulley Sheave Screw Fasteners, lb-ft (Nm) ............... 8.0-11.0 (10.8-14.9)
Governor Plate Counterweight Retaining Pin, lb-ft (Nm) ............... 5.0-7.0 (6.7-9.5)
Oil Pump Assembly Securing Set Screw, lb-ft (Nm) ............... 12.0-15.0 (16.2-20.3)
Connecting Rod Cap Dipper Lock Nut, lb-ft (Nm) ............... 16.0-20.0 (21.6-27.1)
Main Bearing Retainer Plate Cap Bolts, lb-ft (Nm) ............... 15.0-19.0 (20.3-25.7)
Flywheel Alternator Stator Fixed Screws, lb-in (Nm) ............... 30.0-40.0 (3.38-4.51)
Crankcase Breather Body Screw, lb-ft (Nm) ............... 5.0-8.0 (6.7-10.8)
Spark Plug Wire Terminal Nut, lb-in (Nm) ............... 8.0-12.0 (0.90-1.35)

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• Wisconsin Engines Specs
  
• Wisconsin ABN Specs
  
• Wisconsin ACN Specs
  
• Wisconsin AEH Specs
  
• Wisconsin AHH Specs
  

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