Kawasaki FH721D-(L)S01-S 25 HP Horizontal Engine
The Kawasaki FH721D-S01 is a 25-horsepower, 4-stroke OHV V-Twin engine built to deliver commercial-grade power and performance in a compact, lightweight design. Featuring a 1-1/8″ x 3.94″ horizontal shaft, dual-element air cleaner (flat-top design), and a factory-installed muffler, this model is engineered to perform under pressure — whether you’re repowering a John Deere, Scag, Exmark, Toro, or Bad Boy zero-turn mower, or driving another piece of heavy-duty outdoor equipment.
At Carroll Stream Motor Company, we proudly carry the FH721D-S01 as one of Kawasaki’s most trusted engines for both residential and commercial applications. Designed for easy installation and long-term durability, it combines power, reliability, and simplicity for operators who demand consistent performance season after season.
The FH721D-S01 packs 25 horsepower into a 675 cc V-Twin block, offering exceptional torque and smooth operation even under heavy load. Its 4-bolt mounting pattern and horizontal shaft configuration make it ideal for tight engine bays or compact machinery. At just 97 lbs dry weight, this model provides the perfect balance of lightweight handling and industrial-grade output.
Kawasaki’s engineering ensures quiet, efficient combustion and minimal vibration — a key advantage for professional landscapers and equipment owners who rely on consistent power without fatigue or downtime. This model features pressure lubrication with a full-flow oil filter to protect key internal components, ensuring reliable performance over thousands of hours of use. The pulse-driven fuel pump and mechanical governor keep engine performance steady across varying workloads, while the forced-air cooling system maintains optimal temperature in demanding conditions.
The standout feature of this unit — its dual-element Donaldson-style air cleaner — provides superior filtration, preventing dust and debris from entering the intake. This is especially beneficial for mowing, farming, or construction environments where dust and dirt are unavoidable.
Equipped with a 12-volt Bendix-type electric starter and a 15 AMP charging system with regulator, the FH721D-S01 starts instantly in any season. Operators can count on a quick start, consistent idle, and stable acceleration. The engine’s cast-iron cylinder liners and precision-balanced crankshaft further enhance smoothness and service life. Whether you’re a professional landscaper, property manager, or homeowner looking to repower your mower, this Kawasaki engine offers exceptional reliability and the torque you need for the toughest tasks.
We stock a full line of Kawasaki FH and FX series engines, plus replacement parts, tune-up kits, and accessories — so your equipment stays powerful and productive year-round. The Kawasaki FH721D-S01 offers the perfect blend of compact design, high torque, and legendary Kawasaki reliability. It’s built for professionals who need consistent performance, easy starting, and long-term dependability in demanding conditions.
Each image of the engine represents the series itself and not the individual engine.
Features:
Low Tone Muffler
- Equipped with a factory-installed low-tone muffler, specifically engineered to dampen harsh exhaust frequencies and provide a quieter, more professional sound profile during operation.
V-Twin
- Engineered with a 90° V-Twin configuration, this layout provides a naturally balanced power stroke that minimizes internal vibration while delivering high-torque performance for smooth operation.
Horizontal PTO Shaft
- Features a horizontal Power Take-Off (PTO) shaft, making it the ideal choice for heavy-duty equipment like large pressure washers, trenchers, or specialized machinery where the drive connection is side-mounted.
Cast Iron Cylinder Liners
- Built for maximum commercial longevity, the heavy-duty cast iron cylinder sleeves provide a rugged, wear-resistant surface that ensures stable compression and long-term oil control.
Overhead Valves (OHV)
- The overhead valve (OHV) design optimizes engine respiration by placing the valves directly above the piston, resulting in superior thermal efficiency and cooler running temperatures under load.
Float Type Carburetor
- Utilizes a precision float-style carburetor to maintain a consistent fuel level, ensuring reliable throttle response and stable engine performance across various operating angles.
Fixed Main Jet
- Features a factory-calibrated fixed main jet, which ensures the air-fuel ratio remains perfectly tuned for peak performance without the need for manual adjustment.
Pulse Type Fuel Pump
- Includes a vacuum-actuated pulse fuel pump, engineered to provide a consistent and reliable flow of gasoline from the tank to the engine, even during high-demand operation.
Flywheel Magneto Transistor Type Ignition System
- Equipped with a solid-state transistorized ignition system, which uses a high-energy flywheel magneto to generate a consistent spark for maintenance-free operation and rapid starts.
Full Pressure Lubrication System
- Features an automotive-grade full-pressure lubrication system with a high-flow pump that forces oil directly to critical bearings, providing complete protection for the engine's internal components.
Spin-On Oil Filter
- Includes a high-efficiency, spin-on oil filter, allowing for fast and clean oil changes while ensuring microscopic contaminants are removed before they can reach critical engine parts.
Dual Element Air Filter
- Protected by a dual-element air filtration system, which uses both a foam pre-cleaner and a pleated paper filter to provide two layers of defense against dust and airborne debris.
Bendix Type Electric Starter
- Utilizes a Bendix-style electric starter motor, providing positive gear engagement with the flywheel for powerful and reliable engine cranking in all weather conditions.
12v-13a Charging Coil w/ Regulator
- Equipped with a high-output 13-amp charging system and an integrated regulator to maintain battery health and provide steady power for electric clutches and accessories.
75.2 mm Cylinder Bore
- Features a precision-machined 75.2 mm cylinder bore, designed to provide a stable environment for the pistons while contributing to the engine’s $675\text{cc}$ displacement.
76 mm Piston Stroke
- Designed with a 76 mm piston stroke, a configuration that provides the mechanical leverage needed to generate exceptional torque at lower engine speeds.
8.1:1 Compression Ratio
- Engineered with an 8.1:1 compression ratio, offering a perfect balance between high thermal efficiency and the ability to run reliably on standard pump gasoline.
2,400 RPM of Torque
- Specially tuned to reach its peak torque output at 2,400 RPM, ensuring that the engine provides its maximum "pulling power" exactly where the workload is heaviest.
Automatic Compression Release (ACR)
- The automatic compression release mechanism instantly vents internal cylinder pressure during the starting cycle, allowing the engine to turn over effortlessly.
Mechanical Governor
- Features a precision mechanical governor that senses load changes instantly, automatically adjusting the throttle to maintain a steady RPM and consistent power delivery.
Dual Barrel Carburetor with Fuel Shut-Off Solenoid
- Equipped with a dual-barrel carburetor for enhanced air-fuel distribution, along with an electronic fuel shut-off solenoid that prevents "after-fire" by cutting fuel at shutdown.
Electronic Ignition
- Utilizes a high-energy electronic ignition system for precision timing and a hotter spark, resulting in a smoother idle and better fuel efficiency.
Dual Cable Controls
- Designed with a dual-cable control bracket, allowing the operator to manage both the throttle and the choke independently for total control over engine speeds.
