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Wisconsin AHH Engine

The Wisconsin Model AHH is a heavy-duty, single-cylinder, four-cycle, air-cooled gasoline engine manufactured by the Wisconsin Motor Corporation. It stands as the largest displacement single-cylinder engine produced by the company. Designed for industrial, agricultural, and heavy machinery applications, this cast-iron engine features a cast-aluminum head for enhanced heat dissipation. It is recognized as a low-RPM "torque monster" engineered to withstand heavy shock loads due to its robust construction and high-inertia, heavy flywheel. Valve Configuration: Side-valve (L-head) configuration featuring two valves (one intake, one exhaust) located in the cylinder block. Cylinder Bore: 3-5/8 inches (3.625 in). Piston Stroke: 4 inches (4.000 in). Total Displacement: 41.3 cubic inches (approximately 680 cc).

Lubrication System: Constant-level splash lubrication system. Mechanism: An internal plunger pump continuously maintains a precise oil level in a dedicated trough located directly beneath the connecting rod dipper. Cooling System: Forced air-cooled. Mechanism: A combination fan-flywheel draws air and circulates it through a massive sheet-metal shroud. Integrated air ducts and cylinder baffle plates direct the airflow uniformly over the deep cooling fins of the cast-iron cylinder block and the aluminum head.

Fuel System: Equipped with a heavy-duty, cast-iron Zenith or Stromberg updraft carburetor. The carburetor mixes gasoline and air via a mechanical throttle assembly connected to an internal centrifugal flyball governor to automatically maintain engine speed under load. Fuel Delivery: Fuel flows from the main tank through a sediment bowl/fuel strainer to remove debris prior to entering the carburetor bowl. Ignition Integration: A high-tension, externally platform-mounted magneto (Fairbanks-Morse or Wico) features an impulse coupling to provide a hot spark at low cranking speeds for easy hand-crank starting.

General Technical Data

Engine Specifications

Engine Model ............... Wisconsin AHH
Engine Type ............... 4-cycle single-cylinder L-head air-cooled heavy-duty gasoline
Number of Cylinders ............... 1
Engine Bore, in (mm) ............... 3.625 (92.1)
Engine Stroke, in (mm) ............... 4.00 (101.6)
Displacement, cu.in (L) ............... 41.3 (0.68)
Rated Engine Power, hp (kW) ............... 9.2 (6.9)
Rated Engine Speed, rpm ............... 2200
Peak Torque ............... 25.5 lb-ft (34.6 Nm) at 1400 rpm
Governed Speed Range, rpm ............... 1000-2200
Idle Speed, rpm ............... 700-800
Operating Speed, rpm ............... 1400-2200
Compression Ratio ............... 5.1:1-5.5:1
Direction of Rotation ............... Clockwise facing flywheel or cranking end
Power Take-Off Rotation ............... Counter-clockwise facing shaft extension end
Crankcase Breather Type ............... Reed valve type atmospheric ventilation
Muffler Type ............... Cast iron or steel tone silencing expansion chamber
Crankshaft Type ............... Forged steel counterbalanced counter-weighted
Main Bearings Type ............... Tapered roller bearings on both ends
Connecting Rod Material ............... Forged steel with babbit or insert bearing
Camshaft Type ............... Forged steel gear-driven mechanical lift
Valves per Cylinder ............... 2 side valves intake and exhaust L-head
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron removable head
Lubrication System ............... Splash type with plunger oil pump
Oil Pump Type ............... Camshaft-driven reciprocating plunger pump
Oil Filter Type ............... External bypass spin-on optional secondary
Cooling System ............... Forced air-cooled via flywheel blower
Flywheel Fan Type ............... Combination fan-flywheel cast iron vanes
Air Cleaner Type ............... Oil bath or dry dual-element paper
Ignition System ............... High tension magneto with impulse coupling
Starting System ............... Rope start or optional electric starter
Electrical System ............... Magneto ignition or 12V alternator starter

Fuel System

Carburetor Manufacturer ............... Zenith or Marvel-Schebler
Carburetor Type ............... Updraft single-barrel mechanical throttle choke
Carburetor Model Variant ............... Zenith 161 or Marvel-Schebler VH-12
Fuel Pump Type ............... Mechanical diaphragm engine-driven option
Choke Control Type ............... Manual lever with cable remote connection
Throttle Control Type ............... Variable speed governor lever lever assembly
Governor Type ............... Centrifugal flyball mechanical governor
Fuel Tank Capacity, gal (L) ............... 2.75 (10.4)
Fuel Delivery Method ............... Gravity feed or mechanical diaphragm pump
Fuel Type Requirement ............... Low-lead or unleaded automotive gasoline octane 87
Fuel Strainer Type ............... Sediment bowl with fine mesh screen shutoff valve
Main Jet Specification ............... Adjustable needle valve high speed circuit
Idle Jet Specification ............... Fixed low speed circuit with air adjustment screw
Choke Bore Diameter, in (mm) ............... 1.00 (25.4)
Throttle Bore Diameter, in (mm) ............... 1.125 (28.6)
Float Setting Height, in (mm) ............... 1.296 (32.9)
Fuel Line Material ............... Copper tubing or braided flexible line steel lines
Governor Linkage ............... Solid steel rod with spring compensation anti-backlash
High Speed Needle Setting ............... 1.25 turns open from closed seat
Idle Speed Needle Setting ............... 1.00 turns open from closed seat
Air Cleaner Connection Diameter, in (mm) ............... 2.25 (57.2)

Dimensions and Weight

Overall Height, in (mm) ............... 27.5 (700)
Overall Width, in (mm) ............... 21.3 (540)
Overall Length, in (mm) ............... 22.0 (560)
Dry Weight, lbs (kg) ............... 195 (88.5)
Shipping Weight, lbs (kg) ............... 245 (111)

Maintenance Data

Service Information

Maximum Cylinder Pressure, psi (bar) ............... 450 (31.0)
Compression Pressure at Cranking Speed, psi (bar) ............... 75-90 (5.1-6.2)
Oil Pump Output Pressure, psi (bar) ............... 5-15 (0.34-1.03)
Magneto Model Options ............... Wico XH-1 or Fairbanks-Morse FM-X1
Spark Plug Gap, in (mm) ............... 0.030 (0.76)
Magneto Point Gap, in (mm) ............... 0.015 (0.38)
Ignition Spark Timing, deg ............... 23.0 BTDC
Intake Valve Clearance (Cold), in (mm) ............... 0.008 (0.203)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.016 (0.406)

Engine Oil

Engine Oil Type .................. SAE 30, SAE 20W, or SAE 10W
API Service Classifications ......................... SE, SF, SG, or CC
Oil Sump Capacity, qt (L) ............... 2.25 (2.13)
Oil Bath Reservoir Capacity, pt (L) ............... 0.50 (0.24)
Reduction Gear Case Oil Capacity, pt (L) ............... 1.00 (0.47)

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 50 hours
Flush/Clean fuel tank ............... Every 500 hours
Change reduction gear oil ............... Every 500 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 3.625-3.626 (92.07-92.10)
Cylinder Bore Maximum Out of Round, in (mm) ............... 0.002 (0.051)
Cylinder Bore Maximum Taper, in (mm) ............... 0.003 (0.076)
Connecting Rod Length Center to Center, in (mm) ............... 7.50 (190.5)
Connecting Rod Journal Clearance, in (mm) ............... 0.001-0.0025 (0.025-0.063)
Connecting Rod Side Play, in (mm) ............... 0.005-0.010 (0.127-0.254)
Crankshaft Crankpin Journal Diameter, in (mm) ............... 2.250 (57.15)
Crankshaft Main Journal Diameter, in (mm) ............... 2.0625 (52.38)
Crankshaft End Play, in (mm) ............... 0.004-0.006 (0.101-0.152)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.0045-0.0055 (0.114-0.140)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.8755 (22.23)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0001-0.0003 (0.0025-0.0076)
Piston Pin to Con Rod Bushing Clearance, in (mm) ............... 0.0004-0.0008 (0.010-0.020)
Top Ring Groove Side Clearance, in (mm) ............... 0.0020-0.0035 (0.051-0.089)
Second Ring Groove Side Clearance, in (mm) ............... 0.0015-0.0030 (0.038-0.076)
Third 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) ............... 0.0120-0.0170 (0.305-0.431)
Second Ring End Gap, in (mm) ............... 0.0120-0.0170 (0.305-0.431)
Third Ring End Gap, in (mm) ............... 0.0120-0.0170 (0.305-0.431)
Oil Ring End Gap, in (mm) ............... 0.0120-0.0170 (0.305-0.431)
Cylinder Head Flatness Distortion, in (mm) ............... 0.003 (0.076)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.002-0.0035 (0.051-0.089)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0035-0.005 (0.089-0.127)
Valve Guide Inside Diameter, in (mm) ............... 0.375-0.376 (9.525-9.550)
Valve Guide Protrusion Above Block Deck, in (mm) ............... 1.0625 (26.98)
Valve Face Angle, deg ............... 45.0
Valve Seat Angle, deg ............... 45.0
Valve Seat Width, in (mm) ............... 0.0625-0.0937 (1.58-2.38)
Valve Head Margin Thickness, in (mm) ............... 0.0312 (0.79)
Valve Spring Free Length, in (mm) ............... 2.125 (53.97)
Camshaft Journal Diameter (Front), in (mm) ............... 1.375 (34.9)
Camshaft Journal Diameter (Rear), in (mm) ............... 1.250 (31.7)
Camshaft Journal Clearance, in (mm) ............... 0.0015-0.003 (0.038-0.076)
Camshaft End Play, in (mm) ............... 0.002-0.004 (0.051-0.101)
Timing Gear Backlash, in (mm) ............... 0.002-0.004 (0.051-0.101)
Valve Lifter Guide Hole Inside Diameter, in (mm) ............... 0.562-0.563 (14.27-14.30)
Valve Lifter Stem Radial Clearance, in (mm) ............... 0.001-0.0025 (0.025-0.063)

Tightening Torques

Cylinder Head Capscrews, lb-ft (Nm) ............... 22-24 (29.8-32.5)
Connecting Rod Cap Nuts, lb-ft (Nm) ............... 22-24 (29.8-32.5)
Main Bearing Capscrews, lb-ft (Nm) ............... 24-26 (32.5-35.2)
Flywheel Retaining Nut, lb-ft (Nm) ............... 80-90 (108.4-122.0)
Crankcase Oil Base Mounting Screws, lb-ft (Nm) ............... 6-8 (8.1-10.8)
Gear Cover Plate Attaching Screws, lb-ft (Nm) ............... 8-10 (10.8-13.5)
Spark Plug Installation, lb-ft (Nm) ............... 25-30 (33.9-40.6)
Magneto Assembly Mounting Nuts, lb-ft (Nm) ............... 14-16 (19.0-21.7)
Carburetor Flange Mounting Nuts, lb-ft (Nm) ............... 12-14 (16.3-19.0)
Intake Exhaust Manifold Screws, lb-ft (Nm) ............... 16-18 (21.7-24.4)
Governor Housing Assembly Fasteners, lb-ft (Nm) ............... 8-10 (10.8-13.5)
Flywheel Shroud Sheet Screws, lb-ft (Nm) ............... 5-7 (6.8-9.5)
Cylinder Baffle Deflector Fasteners, lb-ft (Nm) ............... 4-6 (5.4-8.1)
Oil Pump Body Capscrew, lb-ft (Nm) ............... 10-12 (13.5-16.3)
Oil Drain Plug, lb-ft (Nm) ............... 20-25 (27.1-33.9)
Fuel Tank Support Bracket Mounting Bolts, lb-ft (Nm) ............... 14-16 (19.0-21.7)
Clutch Back Plate Mounting Bolts, lb-ft (Nm) ............... 22-24 (29.8-32.5)
Reduction Housing Cover Bolts, lb-ft (Nm) ............... 16-18 (21.7-24.4)
Valve Cover Plate Sealing Nut, lb-ft (Nm) ............... 4-5 (5.4-6.8)
Air Cleaner Mounting Bracket Screw, lb-ft (Nm) ............... 5-6 (6.8-8.1)
Breather Assembly Screw Nut, lb-ft (Nm) ............... 3-4 (4.1-5.4)
Crankshaft Tapered Roller Bearing Cover, lb-ft (Nm) ............... 18-20 (24.4-27.1)
Governor Lever Clamp Bolt, lb-ft (Nm) ............... 6-8 (8.1-10.8)
Intermittent Auxiliary Mounting Screws, lb-ft (Nm) ............... 12-15 (16.3-20.3)
Primary Drive Gear Lock Nut, lb-ft (Nm) ............... 45-50 (61.0-67.8)
Magneto Impulse Coupling Trip Nut, lb-ft (Nm) ............... 10-12 (13.5-16.3)
Fuel Pump Blanking Cover Plate Screws, lb-ft (Nm) ............... 6-8 (8.1-10.8)

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• Wisconsin Engines Specs
  
• Wisconsin AB Specs
  
• Wisconsin ABN Specs
  
• Wisconsin ACN Specs
  
• Wisconsin AEH Specs
  

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