The Kubota B7100HST is a legendary compact utility tractor produced by Kubota Corporation from 1977 to 1984. Known for its rugged build and versatility, this machine is powered by the reliable Kubota D750-AH three-cylinder, liquid-cooled diesel engine. With a displacement of 742 cc (46.5 cu-in), this 16.2 PS (11.9 KW; 16.0 HP) at 2,800 rpm motor delivers steady performance, reaching its peak torque of 43.1 Nm (4.4 kg·m; 31.81 lbf·ft) at 1,800 rpm.
A key feature of the B7100 HST is its hydrostatic transmission, offering infinite 2-range forward and reverse gears. This setup allows for smooth speed control, ranging from 5.6 to 14.5 km/h (3.5–9.0 mph) in forward motion, making it ideal for precise landscaping and small farm tasks.
The tractor was available in two main driveline configurations:
- B7100HST-E: Two-wheel drive variant (4×2 2WD).
- B7100HST-D: Four-wheel drive variant (4×4 MFWD).
Built for durability, the B7100 HST features manual steering, differential mechanical expanding shoe brakes, and a closed-center hydraulic system. It comes standard with an open operator station, though a two-post fixed rollover protective structure (ROPS) was offered as an optional safety upgrade.
General specifications
| Kubota B7100 HST General Data | |
| Model | Kubota B7100 HST |
| Tractor type | Сompact utility tractor |
| Production years | 1977-1984 |
| Manufacturer | Kubota |
| Factory | Japan |
| Dimensions and weight | |
| Length | 2,120 mm (83.8 in.) |
| Width | 1,010 mm (40.1 in.) |
| Height (steering wheel) |
2WD: 1,170 mm (46.1 in.) 4WD: 1,180 mm (46.7 in.) |
| Wheelbase |
2WD: 1,380 mm (54.7 in.) 4WD: 1,390 mm (55.1 in.) |
| Ground clearance |
2WD: 250 mm (10.2 in.) 4WD: 240 mm (9.5 in.) |
| Front tread |
2WD: 690 mm (27.4 in.) 4WD: 850 mm (33.5 in.) |
| Weight |
2WD: 522 kg (1,151 lb.) 4WD: 573 kg (1,265 lb.) |
| Fluid capacity | |
| Fuel tank capacity | 12.9 liters (3.4 US gal, 2.8 Imp. gal) |
| Oil capacity | 3.9 liters (4.1 US.qts, 3.4 Imp. qts) |
| Coolant capacity | 4.6 liters (4.9 US.qts, 4.0 Imp. qts) |
| Front axle differential case | 1.5 liters (1.6 US.qts, 1.3 Imp. qts) |
| Front axle gear case | 0.5 liters (0.5 US.qts, 0.45 Imp. qts) |
| Hydraulic luid capacity: | 13.6 liters (3.6 US gal, 3 Imp. gal) |
| Electrical system | |
| Ground | Negative |
| Battery | 12V 45Ah |
| Cabin type | |
| Cabin type |
Standard: Open operator station Optional: Two-post fixed ROPS (Rollover protection structure) |
Engine
The Kubota D750-AH is a compact, three-cylinder diesel engine known for its high power-to-weight ratio and reliability in professional agricultural equipment. Unlike generic diesel motors, the D750-AH features a spherical combustion chamber design, which significantly improves fuel-air mixing and combustion efficiency.
For reliable operation in harsh conditions, the engine is equipped with a pressurized cooling system and forced lubrication. Starting is supported by 12V glow plugs, making it dependable for cold-weather starts. The counterclockwise PTO shaft rotation (viewed from the shaft side) is a critical spec for matching implements and attachments correctly.
Detailed service limits, torque settings, and internal clearances are provided in the technical tables below.
| Kubota D750-AH Engine Specifications | |
| Engine model | Kubota D750-AH |
| Engine type | 4-stroke, vertical, three-cylinders |
| Displacement | 742 cm3, (45.3 cu·in) |
| Cylinder bore: | 68.0 mm (2.68 in) |
| Piston stroke: | 70.0 mm (2.76 in) |
| Compression ratio: | 22.0:1 |
| Max. horsepower |
Gross: 16.2 PS (11.9 KW; 16.0 HP) at 2,800 rpm At PTO-shaft: 13.2 PS (9.7 KW; 13.0 HP) at 2,800 rpm |
| Max. torque | 43.1 Nm (4.4 kg·m; 31.81 lbf·ft) at 1,800 rpm |
| Cooling system | Liquid-cooled |
| Lubricating system | Forced lubrication by pump |
| Combustion chamber | Spherical type |
| Fuel injection pump | Bosch K Type Mini Pump |
| Injection type | Indirect injection |
| Injection nozzle | Bosch throttle type |
| Firing order | 1-2-3 |
| Fuel used | Diesel fuel No.2-D |
| Starting system | Electric starter (12V, 0.8 kW) |
| Starting support device | Glow plug in combustion chamber |
| Governor | Centrifugal ball mechanical governor |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
| Cylinder compression pressure | |
| Cylinder compression: | 31.5 kgf/cm2 (3.09 MPa, 448 psi) |
| Compression differential limit between cylinders: | 10% or less |
| Valve clearance | |
| Intake valve clearance: | 0.150-0.200 mm (0.006-0.008 in) |
| Exhaust valve clearance: | 0.150-0.200 mm (0.006-0.008 in) |
| Oil system | |
| Lubrication system: | Forced lubrication by pump |
| Oil type: | API CC or better |
| Oil capacity: | 3.9 liters (4.1 US.qts, 3.4 Imp. qts) |
| Oil filter: | Full flow paper filter (cartridge type) |
| Oil pressure: |
At idle speed: 68 kPa (0.7 kgf/cm2, 10 psi) At rated speed: 196-441 kPa (2.0-4.5 kgf/cm2, 29-64 psi) |
| Fuel system | |
| Fuel injection pump | Bosch K Type Mini Pump |
| Injection nozzle | Bosch throttle Type |
| Injection timing: | 25° B.T.D.C. |
| Fuel injection pressure | 13.73-14.71 MPa (140-150 kgf/cm2, 1991-2133 psi) |
| Cooling system | |
| Type: | Pressurized radiator, forced circulation with water pump |
| Thermostat’s valve opening temperature: | 80.5-83.5°C (176.9-182.3°F) |
| Temperature at which thermostat completely opens: | 95°C (203°F) |
| Coolant capacity | 4.6 liters (4.9 US.qts, 4.0 Imp. qts) |
| Cylinder block | |
| Number of piston rings (compression / oil): | 2 / 1 |
| Cylinder inner diameter: | 68.000-68.019 mm (2.6772-2.6779 in) |
| Piston skirt to cylinder clearance | 0.076-0.102 mm (0.003-0.004 in) |
| Piston ring side clearance (Second): | 0.085-0.112 mm (0.0033-0.0044 in) |
| Piston ring side clearance (Oil): | 0.020-0.055 mm (0.0008-0.0022 in) |
| Piston ring end gap (Top): | 0.250-0.400 mm (0.0098-0.0157 in) |
| Piston ring end gap (Second): | 0.250-0.400 mm (0.0098-0.0157 in) |
| Piston ring end gap (Oil): | 0.200-0.400 mm (0.0079-0.0157 in) |
| Piston pin outer diameter | 20.002-20.011 mm (0.7875-0.7878 in) |
| Crankshaft main journal diameter: | 43.934-43.950 mm (1.7297-1.7303 in) |
| Crankshaft main journal bearing clearance: | 0.034-0.106 mm (0.0013-0.0042 in) |
| Crankshaft crankpin diameter: | 36.959-36.975 mm (1.4551-1.4557 in) |
| Crankshaft crankpin bearing clearance: | 0.029-0.087 mm (0.0011-0.0034 in) | Crankshaft crankpin side clearance: | 0.200-0.400 mm (0.008-0.016 in) | Crankshaft end play: | 0.150-0.300 mm (0.006-0.012 in) |
| Piston pin diameter: | 20.002-20.011 mm (0.7875-0.7878 in) |
| Piston pin clearance: | 0.015-0.040 mm (0.0006-0.0015 in) |
| Cylinder head | |
| Valves: | 6 (2 valves per cylinder) |
| Valve seat width (INTAKE): | 2.120 mm (0.0835 in) |
| Valve seat width (EXHAUST): | 2.120 mm (0.0835 in) |
| Valve face angle: | 45° |
| Valve seat angle: | 2.120 mm (0.0835 in) |
| Valve stem diameter (INTAKE): | 6.960-6.975 mm (0.274-0.2746 in) |
| Valve stem diameter (EXHAUST): | 6.960-6.975 mm (0.274-0.2746 in) |
| Valve spring free length (INTAKE): | 35.100-34.800 mm (1.3819-1.3701 in) |
| Valve spring free length (EXHAUST): | 35.100-34.800 mm (1.3819-1.3701 in) |
| Camshaft journal diameter: | 32.934-32.950 mm (1.2966-1.2972 in) |
| Camshaft journal bearing clearance: | 0.050-0.091 mm (0.0020-0.0036 in) |
Drivetrain and Chassis Options
The B7100HST series was engineered with two distinct driveline configurations to match specific farm needs. The B7100HST-E (2WD) is optimized for turf work and light landscaping on flat terrain, offering better fuel efficiency and a tighter turning radius. In contrast, the B7100HST-D (4WD) utilizes a mechanical front-wheel drive (MFWD) system, which is essential for loader work and maintaining traction in muddy or hilly conditions.
Transmission Performance
Unlike the gear-driven models, the HST (Hydrostatic Transmission) version provides seamless speed adjustments via foot pedals.
- Speed Ranges: It features a 2-range setup (High/Low).
- Forward Speed: 5.6 to 14.5 km/h (3.5–9.0 mph).
- Reverse Speed: 3.9 to 10.0 km/h (2.4–6.2 mph).
The manual steering remains responsive, though users should note it requires more effort when a front-end loader is fully taxed. For maximum pulling power, the mechanical rear differential lock can be engaged to prevent one-wheel spin in slippery spots.
| Kubota B7100HST Transmission & Chassis Specs | |
| Chassis | B7100HST-E (4×2 2WD) / B7100HST-D (4×4 MFWD 4WD) |
| Steering | Manual type |
| Differential lock | Mechanical rear |
| Brakes | Differential mechanical expanding shoe |
| Transmission type | Hydrostatic transmission Type I: B7100HST-E (s/n before: 11906), B7100HST-D (s/n before: 51742) Type II: B7100HST-E (s/n and later: 11907), B7100HST-D (s/n and later: 51743) |
| Gears | 2 forward and 2 reverse |
| Ground speed |
Forward: 5.6-14.5 km/h (3.5-9.0 mph) Reverse: 3.9-10.0 km/h (2.4-6.2 mph) |
Difference Between Type I and Type II HST Models
Kubota introduced a major revision to the B7100HST drivetrain around 1980/1981. It is vital to identify your tractor’s serial number before ordering transmission or hydraulic parts.
Type I (Early Models):
- Serial Numbers: B7100HST-E (before 11906), B7100HST-D (before 51742).
- Key Feature: Uses a different hydrostatic pump design. Many internal components, including the cylinder block and valve plates, are specific to this early series and are becoming increasingly difficult to find as new old stock (NOS).
Type II (Late Models):
- Serial Numbers: B7100HST-E (11907 and later), B7100HST-D (51743 and later).
- Key Feature: This is the more “standardized” version of the Kubota HST. The internal porting of the transmission case was improved for better cooling and smoother foot pedal response.
- Oil Filter: The spin-on HST filter (Kubota 15241-32090) is standard here, whereas some very early Type I units had different filtration setups.
Tires
| Kubota B7100HST Tire Options | |
| Front tires |
Agricultural: 6.9-9 (2WD), 6-12 (4WD) Lawn and turf: 20.5×8.0-10 |
| Rear tires |
Agricultural: 8.3-16 Lawn and turf: 29×12.0-15 |
| Nornal tire pressure | |
| Front tires | 0.10 MPa (1.0 kgf/cm2, 14 psi) |
| Rear tires | 0.12 MPa (1.2 kgf/cm2, 18 psi) |
Wheel Bolt Pattern & Rim Specs
When replacing rims or sourcing second-hand wheels for the Kubota B7100HST, it is critical to verify the bolt pattern and center pilot hole diameter. Standard trailer rims may look similar but often fail to fit the proprietary Kubota hubs.
- Front Wheels (4WD/2WD): Most B7100 models utilize a 4-lug pattern on a 100 mm (3.94″) Bolt Circle (PCD) with a 70 mm (2.75″) pilot hole. Note that some late-production units or modified hubs might feature a 6-lug front setup.
- Rear Wheels: These tractors standardly use a 6-lug pattern on a 152.4 mm (6.0″) Bolt Circle (PCD) with a 117.5 mm (4.625″) pilot hole.
- Maintenance Tip: Always re-torque lug nuts after the first 10 hours of operation following a wheel change.
Recommended torque settings:
- Front: 47–54 Nm (35–40 ft-lbs).
- Rear: 108–122 Nm (80–90 ft-lbs).
| Position | Drive Type | Bolt Pattern (Lugs) | Bolt Circle (PCD) | Pilot Hole (Center) |
| Front | 4WD | 4 Lugs | 100 mm (approx. 4″) | 70 mm (2.75 in) |
| Front | 2WD | 4 Lugs | 100 mm (approx. 4″) | 70 mm (2.75 in) |
| Rear | All | 6 Lugs | 152.4 mm (6.0 in) | 117.5 mm (4.625 in) |
PTO and 3-point linkage
The Kubota B7100 series is equipped with a rear power take-off (PTO) system, which is integral for powering various implements like mowers, tillers, and other attachments. The rear PTO is a transmission-driven type, which means it’s mechanically linked to the engine through the tractor’s transmission system, allowing for efficient power transfer. The PTO speed is versatile, with options for 540, 750, or 1,000 rpm, offering flexibility for different implements that require specific operational speeds. Additionally, the rear PTO can run at 2,500 rpm for high-speed applications, while the front PTO is capable of reaching up to 2,800 rpm, providing high power output for front-mounted attachments.
In terms of lifting and attachment capabilities, the B7100 series features a Category I 3-point linkage system, which is a standard for compact tractors. This linkage system allows for easy attachment and detachment of implements such as plows, harrows, and other farming tools. The hydraulic lift system ensures that the 3-point linkage can raise and lower attachments smoothly and efficiently, with a maximum lifting capacity of 181 kg (400 lbs) at the link ends. This lifting capacity makes the B7100 versatile enough to handle a range of light to moderate-duty implements, making it suitable for a variety of agricultural tasks.
| PTO (Power take-off shaft) | |
| PTO Type: | Rear, transmission |
| PTO Speed: |
Rear: 540 / 750 / 1,000 rpm Rear: 2,500 rpm Front: 2,800 rpm |
| Hydraulic lift | |
| 3-point linkage: | Category I |
| Control system: | – |
| No. of remote valves: | – |
| Max lifting capacity (at link end): | 181 kg (400 lb) |
Hydraulic system
| Hydraulic system | |
| Type: | Closed center |
| Hydraulic luid capacity: | 13.6 L (3.6 gal.) |
| Hydraulic flow: | 11.4 lpm (3.0 gpm) |
Attachments
| Kubota RC54-71B: 54″ mid-mount mower deck with 3-blade and hydraulic lift | |
| Cutting width: | 1,372 mm (54.0 in) |
| Cutting height: | 38.0 to 102.0 mm (1.5 to 4.0 in) |
| Weight: | 148.0 kg (327 lbs) |
| Kubota RC60-71B: 60″ mid-mount mower deck with 3-blade and hydraulic lift | |
| Cutting width: | 1,524 mm (60.0 in) |
| Cutting height: | 38.0 to 102.0 mm (1.5 to 4.0 in) |
| Weight: | 168.0 kg (371 lbs) |
| Kubota B222: 48″ front-mount two-stage snow blower | |
| Cleaning width: | 1,210 mm (48.0 in) |
| Cleaning height: | 580 mm (23.0 in) |
| Kubota B1630C Loader | |
| Height (at pin) | 1,710 mm (67.7 in) |
| Lift (full at pin) | 231 kg (510 lbs) |
| Breakout | 353 kg (780 lbs) |
| Dump angle | 46° |
| Rollback angle (ground line) | 28° |
| Dump reach | 510 mm (20.25 in) |
| Ground reach | 1,220 mm (48.3 in) |
| Dump clearance | 1,300 mm (51.5 in) |
| Bucket width | 1,210 mm (48 in) |
Serial numbers
| Serial numbers (Location on clutch housing, left side) | |
| 1980 | 10001 |
| 1981 | 11035 |
| 1982 | 13305 |
| 1983 | 51426 |
| 1984 | 53433 |
Maintenance Parts & Consumables List
To keep your Kubota B7100HST running at peak performance, use the following part specifications for regular maintenance:
- Engine Oil Filter: Full-flow paper cartridge type (Spin-on).
- Common replacements: Kubota 15853-32430, Baldwin B179, Wix 51064.
- HST Hydraulic Oil Filter: Special high-pressure spin-on filter.
- Common replacements: Kubota 15241-32090, 15241-32094, Baldwin BT8488, Wix 51521.
- Fuel Filter: Element type.
- Common replacements: Kubota 15221-43170, Baldwin PF933, Wix 33262.
- Air Filter: Dry element type.
- Common replacements: Kubota 15222-11220, Baldwin PA1864, Wix 42276.
- Fan Belt: V-type belt.
- Specifications: Standard industrial size (approx. 32-35 inches depending on alternator setup).
- Glow Plugs: 12V quick-heat type.
- Part number: Kubota 15221-65510 (NGK Y-103V or equivalent).
- Battery: 12V 45Ah (Group 24 or similar compact tractor size).
- Tires:
- Front (4WD): 6-12 (Ag) or 20.5×8.0-10 (Turf).
- Rear (4WD): 8-16 (Ag) or 29×12.0-15 (Turf).
Recommended Lubricants
- Engine Oil: 10W-30 or 15W-40 (API Service CC, CD or higher).
- Transmission/Hydraulic Fluid: (MUST use HST-compatible fluid) Kubota Super UDT-2 is highly recommended for smoother hydrostatic operation.
- Alternatives: Mobil Fluid 424, Chevron 1000 THF (Must meet Kubota UDT specifications).
- Front Axle (4WD): SAE 80W-90 Gear Oil.
- Chassis Grease: Multi-purpose lithium-based grease (NLGI No. 2).
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