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Honda V-Twin Horizontal OHV Engine with Electric Start – 688cc, GX Series, 1 1/8in. x 3 31/32in. Shaft, Model# GX660RHTAF

Item# 166138
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Honda V-Twin Horizontal OHV Engine with Electric Start – 688cc, GX Series, 1 1/8in. x 3 31/32in. Shaft, Model# GX660RHTAF

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Only $1399.99
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  • 688cc air-cooled, 4-stroke OHV engine
  • 50-state compliant engine
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Product Summary

With experience born on the raceways and roadways and a dedication to innovation, there's plenty of reasons to insist on the new Honda GX660 V-Twin engine. There's superior engine design, with a 90° configuration that reduces vibration and allows a compact footprint. There's superior construction, with a forged steel crankshaft and an integrated cylinder head. Fewer parts means better durability. There's a digital CDI ignition coil that ensures improved fuel economy and lowered emissions. There's even improved air cleaning, meaning that you can wait 5 times longer between filter changes. Honda even gives their engines a 3-year limited warranty.

What's Included
  •  (1) Engine, Model# GX660RHTAF

Features + Benefits

  • 688cc air-cooled, 4-stroke OHV engine
  • 50-state compliant engine
Key Specs
Item# 166138
Brand Honda Engines
Manufacturer's Warranty 3 year limited warranty
Ship Weight 110.0 lbs
Engine Displacement (cc) 688
Start Type Electric, shift type
Application Grain auger/elevator, pressure washer, semi-trailer w/power pack
Engine Type GX series OHV V-Twin commercial-duty
Net Power Output (HP) 21.5 (16.0 kW) at 3,600 RPM
Net Torque (lbs./ft.) 35.6 (48.3 Nm) at 2,500 RPM
Shaft Output Horizontal
Crankshaft T type
Shaft Diameter (in.) 1 1/8
Shaft Length (in.) 3 31/32
Shaft Keyway (in.) 1/4, (Key size 6.3mm x 70mm)
Shaft End Tapped (Diameter (in.)/Threads per inch) 7/16–20, UNF2B
Shaft Rotation (From PTO Shaft Side) Counterclockwise
PTO Height (in.) 5 1/4
Cylinders (qty.) 2
Cylinder Bore Integrated
Bore x Stroke (in.) 3.1 x 2.8
Compression Ratio 9.3:1
Cooling System Air cooled
Air Cleaner Type Dual element/cylindrical
Fuel Tank Not included
Fuel Type Gasoline
Fuel Pump Boost type
Oil Capacity (qt.) 2
Lubrication System Full pressure
Low Oil Alert Yes
Ignition System Electonic, digital CDI w/variable ignition timing
Governor System Mechanical
Carburetor 2-barrel, fuel cut solenoid, inner vent
Throttle Control Manual
Choke Control Manual
Max. RPM 3,600
Charging System Amps 20
Muffler Included Not included
Flywheel Brake No
Bolt Circle (in.) 5, 6 1/2, 7 3/4
Mounting Base L x W (in.) 7 11/16 x 3 25/64–4 21/32
Dimensions L x W x H (in.) 15 7/8 x 16 1/8 x 17 3/16
EPA/CARB Approval (California Air Resource Board) Yes

Customer Reviews

Product Question + Answer
Accessories Frequently Purchased with this Item

You'll Need

Mufflers

High-Mount Muffler for Honda V-Twin Engines — Fits GX630, 660 and 690 Engines, Right/Oil Filter Side Mount, Model# MUF-0560.SIL
High-Mount Muffler for Honda V-Twin Engines — Fits GX630, 660 and 690 Engines, Right/Oil Filter Side Mount, Model# MUF-0560.SIL
Item# 601099
Factory Shipped —
Estimated Delivery: 5 - 7 Business Days
Only $139.99
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High-Mount Muffler for Honda V-Twin Engines — Fits GX630, 660 and 690 Engines, Left/Starter Side Mount, Model# MUF-0560R.SIL
High-Mount Muffler for Honda V-Twin Engines — Fits GX630, 660 and 690 Engines, Left/Starter Side Mount, Model# MUF-0560R.SIL
Item# 601105
Factory Shipped —
Estimated Delivery: 5 - 7 Business Days
Only $139.99
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Replacement Parts
Call To Order: 1-800-657-0516

Mon - Fri 7:00 AM - 6:00 PM (Central)
Sat 7:00 AM - 3:00 PM (Central)

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Honda V-Twin Horizontal OHV Engine with Electric Start – 688cc, GX Series, 1 1/8in. x 3 31/32in. Shaft, Model# GX660RHTAF The price is $1,399.99.
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Hide Similarities
Engine Displacement (cc)
688 688 688 688 688
Start Type
Electric start Electric, shift type Electric, shift type Electric, shift type Electric
Application Concrete saw, pressure washer, chipper/shredder, trencher, vibratory roller, ride-on cement trowel Grain auger/elevator, pressure washer, semi-trailer w/power pack Lawn tractor, mower, utility vehicle, concrete saw, pressure washer, chipper/shredder, trencher, vibratory roller, ride-on cement trowel Utility vehicle, concrete saw, pressure washer, chipper/shredder Pressure washer, lawn/garden equipment, generator, small vehicle, water pump
Engine Type GX series OHV V-Twin commercial-duty GX series OHV V-Twin commercial-duty GX series OHV V-Twin commercial-duty GX series OHV V-Twin commercial-duty GX series OHV V-Twin
Net Power Output (HP) 20.8 (15.5 kW) at 3,600 RPM 21.5 (16.0 kW) at 3,600 RPM 21.5 (16.0 kW) at 3,600 RPM 21.5 (16.0 kW) at 3,600 RPM 22.1 (16.5 kW) at 3,600 RPM
Net Torque (lbs./ft.) 35.6 (48.3 Nm) at 2,500 RPM 35.6 (48.3 Nm) at 2,500 RPM 35.6 (48.3 Nm) at 2,500 RPM 35.6 (48.3 Nm) at 2,500 RPM 35.6 (48.3 Nm) at 2,500 RPM
Shaft Output
Horizontal Horizontal Horizontal Horizontal Horizontal
Crankshaft Q-type T type T type B-type T type
Shaft Diameter (in.) 1 1 1/8 1 1/8 1 7/16 1 1/8
Shaft Length (in.) 2 29/32 3 31/32 3.55 4 7/16 2 29/32
Shaft Keyway (in.)
1/4, (Key size 6.3mm x 50mm) 1/4, (Key size 6.3mm x 70mm) 1/4, (Key size 6.3mm x 70mm) 1/4 (key size 6.3mm x 70mm) 1/4 (key size 6.3mm x 70mm)
Shaft End Tapped (Diameter (in.)/Threads per inch) 3/8–24, UNF2B 7/16–20, UNF2B 7/16–20, UNF2B 5/8-18 UNF2B 7/16–20, UNF2B
Shaft Rotation (From PTO Shaft Side) Counterclockwise Counterclockwise Counterclockwise Counterclockwise Counterclockwise
PTO Height (in.)
5 1/4 5 1/4 5 1/4 5 1/4 5 1/4
Bearing Type
- - - Ball bearing Ball bearing
Cylinders (qty.)
2 2 2 2 2
Cylinder Bore
Integrated Integrated Integrated Cast iron Integrated
Bore x Stroke (in.)
3.1 x 2.8 3.1 x 2.8 3.1 x 2.8 3 1/16 x 2 13/16 78 x 72
Compression Ratio
9.3:1 9.3:1 9.3:1 9.3:1 9.3:1
Cooling System
Air cooled Air cooled Air cooled Air cooled Air cooled
Air Cleaner Type
Dual element/cylindrical Dual element/cylindrical Dual element/cylindrical Dual element Dual element
Fuel Tank Not included Not included Not included Not included No
Fuel Type Gasoline Gasoline Gasoline Gasoline Gas
Fuel Pump
Boost type Boost type Boost type Boost type Boost type
Fuel Filter
- - - Yes Fuel strainer
Oil Capacity (qt.)
2 2 2 2 2.1
Lubrication System
Full pressure Full pressure Full pressure Forced lubrication Forced lubrication
Low Oil Alert
Yes Yes - - No
Low Oil Shutdown
- - - - No
Ignition System
Electonic, digital CDI w/variable ignition timing Electonic, digital CDI w/variable ignition timing Electonic, digital CDI w/variable ignition timing Digital CDI w/variable timing Electrical, digital CDI w/variable ignition timing
Governor System
Mechanical Mechanical Mechanical Mechanical Mechanical
Carburetor
2-barrel, fuel cut solenoid, inner vent 2-barrel, fuel cut solenoid, inner vent 2-barrel, fuel cut solenoid, inner vent Horizontal, two-barrel butterfly valve, internal vent Horizontal, two-barrel butterfly valve, internal vent
Throttle Control
Manual Manual Remote (wire) Remote (wire) Remote
Choke Control
Manual Manual Remote (wire) Remote (wire) Remote
Max. RPM
3,600 3,600 3,600 3,600 3,600
Charging System Amps 2.7 20 20 17 20
Muffler Included
Not included Not included Not included Not included No
Flywheel Brake
No No No - No
Auto Compression Release
- - - Yes Yes
Bolt Circle (in.)
5, 6 1/2, 7 3/4 5, 6 1/2, 7 3/4 5, 6 1/2, 7 3/4 5, 6 1/2, 7 3/4 5, 6 1/2, 7 3/4
Mounting Base L x W (in.)
7 11/16 x 3 25/64–4 21/32 7 11/16 x 3 25/64–4 21/32 7 11/16 x 3 25/64–4 21/32 7 11/16 x 3 25/64–4 21/32 7 11/16 x 3 25/64–4 21/32
Dimensions L x W x H (in.)
15 7/8 x 16 1/8 x 17 3/16 15 7/8 x 16 1/8 x 17 3/16 15 7/8 x 16 1/8 x 17 3/16 15 7/8 x 16 1/8 x 17 3/16 15 9/10 x 16 1/10 x 17 1/5
EPA/CARB Approval (California Air Resource Board)
Yes Yes Yes Yes Yes