BMW R 18 / R 18 Classic (K34) — OEM Fluid, Tire Pressure & Maintenance Specs
1,802cc Air/Oil-Cooled Flat-Twin OHV Pushrod Big Boxer (Dry Clutch + Exposed Shaft) · Source: BMW Motorrad R 18 (K34 / 0L11) Official Rider’s Manual Specifications
According to the BMW Motorrad R 18 (K34 / 0L11) Official Rider’s Manual Specifications, the 2020–Present BMW R 18 / R 18 Classic (K34) (chassis K34 (R 18 / Classic)/0L11/K35 (R 18 B / Transcontinental)) requires 3.7 L (3.91 US qt) of SAE 15W-50 (JASO MA2, API SJ / JASO MA2 (BMW Advantec Pro 15W-50)) engine oil for a drain-only change and 4 L (4.23 US qt) with filter service (11427673541 / 11425B79146 (HF164)). Standard solo cold tire pressure is 250 kPa / 2.50 bar / 36 PSI front (120/70R19 M/C 60V) and 290 kPa / 2.90 bar / 42 PSI rear (180/65B16 M/C 81H), paired with 4× NGK MAR8AI-10DS (Twin-Spark Big Boxer) spark plug(s) and a BMW 12V 26Ah AGM (Heavy-Duty Cranking) battery.
Drain only: 3.7 L (3.91 US qt)
R 290 kPa (2.90 bar)
Est. Range: ~286 km (178 mi)
1. Engine Lubrication, Filter & Clutch Specifications
| Clutch Architecture | Dry Single-Plate Manual Clutch (Separate Gearbox Oil) |
|---|---|
| Recommended Viscosity & Grade | SAE 15W-50 · JASO MA2 · API SJ / JASO MA2 (BMW Advantec Pro 15W-50) |
| Oil Volume (Drain / With Filter / Overhaul) |
• Drain only: 3.7 L (3.91 US qt) • With filter/strainer: 4 L (4.23 US qt) • Complete dry overhaul: 4.5 L (4.76 US qt) |
| OEM Oil Filter Code & Type | 11427673541 / 11425B79146 (HF164) |
| Correct Oil Level Check Method | Hold bike upright on level ground 3–5 min after warm shutdown; read crankcase sight glass |
| Oil Drain Bolt Torque | 28 N·m (20.7 lb-ft / 2.86 kgf·m) — Use fresh crush washer |
| Separate Transmission / Gearbox Oil | 1150 ml (1.15 L) — SAE 70W-80 Fuchs Titan EG 4218 / Hypoid G3 (1,150 ml separate 6-speed gearbox) |
| Final Drive / Bevel Gear Oil | 210 ml (0.21 L) — SAE 70W-80 Hypoid Axle Oil G3 (210 ml rear bevel gear) |
2. Cold Tire Pressures, Wheels, Ignition & Drivetrain
| Front / Rear OEM Tire Sizes | Front: 120/70R19 M/C 60V · Rear: 180/65B16 M/C 81H (Tube-Type Spoke Rim) |
|---|---|
| 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: 260 kPa / 2.60 bar / 38 PSI Rear: 310 kPa / 3.10 bar / 45 PSI |
| OEM Spark Plug & Quantity | NGK MAR8AI-10DS (Twin-Spark Big Boxer) × 4 (Gap: 1.0 mm) |
| OEM Battery Code & Rating | BMW 12V 26Ah AGM (Heavy-Duty Cranking) (12V 26.0Ah Sealed Heavy-Duty AGM) |
| Final Drive Maintenance | Exposed Nickel-Plated Open Driveshaft — Separate gearbox (1,150 ml) & rear bevel gear (210 ml) |
| Brake Fluid & Coolant | DOT 4 · Air/Oil-Cooled Big Boxer (No liquid coolant — lower-frame oil cooler) |
3. Ergonomics, Range & Scheduled Service Intervals
| Displacement · Max Power · Peak Torque | 1802 cc · 91 hp @ 4,750 rpm · 158 N·m (116.5 lb-ft) @ 3,000 rpm |
|---|---|
| Seat Height & Wet Curb Weight | 690 mm (27.2 in) · 345 kg (761 lbs) |
| Fuel Tank & Est. Real-World Range | 16 L (4.2 US gal) · ~17.9 km/L → ~286 km (178 mi) |
| OEM Scheduled Maintenance Intervals |
• First Break-In: 1,000 km • Engine Oil / Filter: 10,000 km / 10,000 km • Air Filter / Spark Plug: 20,000 km / 20,000 km • Valve Clearance Check: 10,000 km |
4. Generation Cutoffs & Real-World Wrenching Gotchas
Model-Year & Chassis Generation Notes
Inspired by the 1936 R 5, BMW’s largest-ever 1,802cc Big Boxer powers both the cruiser K34 (R 18 / Classic, 16 L tank, 345 kg) and touring K35 (R 18 B / Transcontinental, 24 L tank). Note 2025+ Euro 5+ R 18 cruisers stepped up to an 18-inch rear wheel and 163 N·m.
Oil & Clutch Mechanical Engineering Note
Equipped with a massive dry single-plate anti-hopping clutch, the Big Boxer isolates three distinct lubricants: 4.0 L of SAE 15W-50 in the engine, 1,150 ml of SAE 70W-80 in the 6-speed gearbox, and 210 ml of SAE 70W-80 in the rear bevel drive.
Garage Wrenching Gotchas
- The exposed nickel-plated open driveshaft spins in the elements—rinse road salt or coastal spray promptly and wipe dry to prevent pitting around the exposed U-joint yokes.
- Massive protruding boxer cylinders mandate mid-mounted footpegs (forward controls cannot be fitted), and classic wire-spoke R 18 wheels require inner tubes (cast-alloy wheels are tubeless).
5. Frequently Asked Questions (FAQ)
What are the exact engine, transmission, and final drive oil capacities on the BMW R 18?
1) Engine with filter (11427673541): 4.0 L of SAE 15W-50; 2) Separate 6-speed gearbox: 1,150 ml of SAE 70W-80; 3) Rear bevel-gear final drive: 210 ml of SAE 70W-80 Hypoid G3.
Is valve clearance adjustment easy on the BMW R 18 Big Boxer?
Yes—its protruding OHV pushrod heads use accessible screw-and-locknut valve adjusters rather than shims-under-buckets, making the 10,000 km check straightforward.
What cold tire pressures should I run on the 345 kg BMW R 18?
Run 250 kPa (36 PSI) front / 290 kPa (42 PSI) rear solo cold, increasing to 260 kPa (38 PSI) front / 310 kPa (45 PSI) rear with a passenger or saddlebags.