Harley-Davidson Fat Boy 114 (FLFBS Milwaukee-Eight) — OEM Fluid, Tire Pressure & Maintenance Specs
1,868cc Air/Oil-Cooled 45° V-Twin 8-Valve Milwaukee-Eight 114 Softail (3-Hole) · Source: Harley-Davidson Softail Models (FLFBS Fat Boy 114) Official Owner’s Manual
According to the Harley-Davidson Softail Models (FLFBS Fat Boy 114) Official Owner’s Manual, the 2018–2024 Harley-Davidson Fat Boy 114 (FLFBS Milwaukee-Eight) (chassis FLFBS (114)/FLFB (107)) requires 4.3 L (4.54 US qt) of SAE 20W-50 (JASO MA2, Screamin’ Eagle SYN3 20W-50 / H-D 360 SAE 20W-50) engine oil for a drain-only change and 4.7 L (4.97 US qt) with filter service (HD 62700297 (Chrome) / 62700296 (Black) / HF171C). Standard solo cold tire pressure is 250 kPa / 2.50 bar / 36 PSI front (160/60R18 70V) and 290 kPa / 2.90 bar / 42 PSI rear (240/40R18 79V), paired with 4× HD 6R10 (31600012 — Dual-Plug M8 4V Heads) spark plug(s) and a HD 65989-97E / YTX20HL-BS battery.
Drain only: 4.3 L (4.54 US qt)
R 290 kPa (2.90 bar)
Est. Range: ~344 km (214 mi)
1. Engine Lubrication, Filter & Clutch Specifications
| Clutch Architecture | Wet Multi-Plate Manual Clutch NEVER use JASO MB |
|---|---|
| Recommended Viscosity & Grade | SAE 20W-50 · JASO MA2 · Screamin’ Eagle SYN3 20W-50 / H-D 360 SAE 20W-50 |
| Oil Volume (Drain / With Filter / Overhaul) |
• Drain only: 4.3 L (4.54 US qt) • With filter/strainer: 4.7 L (4.97 US qt) • Complete dry overhaul: 5 L (5.28 US qt) |
| OEM Oil Filter Code & Type | HD 62700297 (Chrome) / 62700296 (Black) / HF171C |
| Correct Oil Level Check Method | At full operating temperature resting ON THE SIDESTAND (Jiffy Stand); thread dipstick in to read |
| Oil Drain Bolt Torque | 24 N·m (17.7 lb-ft / 2.45 kgf·m) — Use fresh crush washer |
| Primary Chaincase Fluid | 1065 ml (1.06 L) — H-D Formula+ Primary & Transmission Fluid (1,065 ml / 36 fl oz wet refill) |
| Separate Transmission / Gearbox Oil | 828 ml (0.83 L) — H-D Formula+ or Heavy Synthetic Gear Oil 80W-140 (828 ml / 28 fl oz refill) |
2. Cold Tire Pressures, Wheels, Ignition & Drivetrain
| Front / Rear OEM Tire Sizes | Front: 160/60R18 70V · Rear: 240/40R18 79V (Tubeless) |
|---|---|
| Cold Tire Pressure — Solo Riding |
Front: 250 kPa / 2.50 bar / 36 PSI Rear: 290 kPa / 2.90 bar / 42 PSI |
| Cold Tire Pressure — 2-Up / Loaded Touring |
Front: 250 kPa / 2.50 bar / 36 PSI Rear: 290 kPa / 2.90 bar / 42 PSI |
| OEM Spark Plug & Quantity | HD 6R10 (31600012 — Dual-Plug M8 4V Heads) × 4 (Gap: 0.8–0.9 mm) |
| OEM Battery Code & Rating | HD 65989-97E / YTX20HL-BS (12V 17.5Ah High-Output AGM (310 CCA)) |
| Final Drive Maintenance | Harley-Davidson Heavy-Duty Carbon Belt — Wide-tire offset rear pulley |
| Brake Fluid & Coolant | DOT 4 · Air/Oil-Cooled Milwaukee-Eight 114 (No coolant — precision oil-cooled cylinder heads) |
3. Ergonomics, Range & Scheduled Service Intervals
| Displacement · Max Power · Peak Torque | 1868 cc · 94 hp @ 5,020 rpm · 155 N·m (114.3 lb-ft) @ 3,000 rpm |
|---|---|
| Seat Height & Wet Curb Weight | 675 mm (26.6 in) · 317 kg (699 lbs) |
| Fuel Tank & Est. Real-World Range | 18.9 L (5.0 US gal) · ~18.2 km/L → ~344 km (214 mi) |
| OEM Scheduled Maintenance Intervals |
• First Break-In: 1,600 km • Engine Oil / Filter: 8,000 km / 8,000 km • Air Filter / Spark Plug: 24,000 km / 48,000 km • Valve Clearance Check: 48,000 km |
4. Generation Cutoffs & Real-World Wrenching Gotchas
Model-Year & Chassis Generation Notes
Redesigned from the ground up in 2018 onto the monoshock Softail chassis with dual-counterbalanced Milwaukee-Eight 114 power and massive 160mm front / 240mm rear Lakester disc wheels (replacing the pre-2018 Twin Cam’s 200mm rear). Note 2025+ Fat Boys stepped up to the M8 117.
Oil & Clutch Mechanical Engineering Note
Milwaukee-Eight Big Twins run Harley’s classic 3-Hole isolated lubrication: 1) Engine (SAE 20W-50, ~4.3–4.7 L with filter 62700297), 2) Primary chaincase & wet clutch (Formula+, 1,065 ml / 36 fl oz), and 3) 6-speed Cruise Drive gearbox (Formula+ or 80W-140 gear oil, 828 ml / 28 fl oz).
Garage Wrenching Gotchas
- Milwaukee-Eight 4-valve heads utilize dual spark plugs per cylinder (4 total
HD 6R10 / 31600012)—reaching the two recessed center plugs requires unbolting and lifting or removing the 5-gallon fuel tank. - With a steamroller
160/60R18front and240/40R18rear on solid Lakester disc wheels, letting cold pressure drop below 36 PSI front / 42 PSI rear causes heavy low-speed counter-steering resistance.
5. Frequently Asked Questions (FAQ)
What are the exact 3-Hole fluid capacities on a Harley-Davidson Fat Boy 114?
1) Engine: ~4.4–4.7 L (up to 5.0 qt nominal) of SAE 20W-50 with filter HF171C; 2) Primary: 1,065 ml (36 fl oz) of Formula+; 3) 6-Speed Transmission: 828 ml (28 fl oz) of Formula+ or 80W-140 gear oil.
Do all three fluids on a Milwaukee-Eight Softail get changed at every service?
Factory schedule calls for engine oil & filter every 8,000 km (5,000 mi), primary fluid every 16,000 km (10,000 mi), and transmission oil every 32,000 km (20,000 mi), after the initial 1,600 km break-in 3-hole service.
How do you adjust rear shock preload on the Softail Fat Boy 114?
Turn the tool-free external hydraulic preload adjuster knob on the right side behind the frame cover according to rider and passenger weight.