Inspected used parts for BMW R75 vintage motorcycles are stocked at Sun Coast Cycle Sports. The R75 designation covers BMW's 750cc Airhead boxer twins produced across the /5 (1969-1973), /6 (1974-1976), and /7 (1976-1977) series, representing one of the most significant chapters in BMW motorcycle history. The R75/5 launched the modern era of BMW boxers with a completely redesigned engine featuring a one-piece forged crankshaft, chain-driven camshaft, electric starter, and unit construction. Every component from our vintage BMW donors is assessed at our Florida shop, photographed under a unique SKU, and listed with free shipping across the continental U.S.
R75 generation and parts compatibility
| Model | Years | Engine | Power | Key Features |
|---|
| R75/5 | 1969-1973 | 745cc air-cooled boxer, 2-valve, Bing carbs | 50 hp | First modern BMW boxer; "toaster" tank; drum brakes; 4-speed |
| R75/6 | 1974-1976 | 745cc air-cooled boxer, 2-valve, Bing carbs | 50 hp | Front disc brake option; 5-speed; new tank and seat design; 280W alternator |
| R75/7 | 1976-1977 | 745cc air-cooled boxer, 2-valve, Bing carbs | 50 hp | Final 750cc Airhead; replaced by R80/7 |
The R75/5 was the first of BMW's "slash" series Airheads, featuring an entirely new engine designed by Hans-Gunther von der Marwitz. The one-piece forged crankshaft with car-type plain bearings, chain-driven camshaft, and electric starter were revolutionary for BMW, which had used gear-driven cams and roller-bearing cranks in the pre-war and /2 era. This basic architecture carried through every Airhead produced from 1969 to 1996.
All three R75 series (/5, /6, /7) use the same 82mm bore and 70.6mm stroke for 745cc displacement. The cylinders, pistons, and heads interchange across all R75 models. The /6 and /7 share most chassis components, while the /5 has unique bodywork (the distinctive "toaster" tank) and a 4-speed gearbox (vs 5-speed on /6 and /7).
Engine cases changed in 1976 from the 97mm cylinder opening (/5 and early /6) to the larger 99mm opening (/7 and later). This means that while R75 cylinders will fit all Airhead cases, larger-displacement cylinders (R90, R100) only fit the later 99mm cases. This is a critical detail when sourcing cases for engine rebuilds or displacement upgrades.
The R75/5 was produced alongside the R50/5 (500cc) and R60/5 (600cc). Within any given production year, the only differences between displacement variants are the cylinders, pistons, and carburetors. Transmissions, frames, and most accessories interchange within each slash series.
Common R75 failure points and replacement parts
Points ignition (all models): All R75 models use mechanical points ignition. Points require regular adjustment (every 3,000-5,000 miles) and periodic replacement. Electronic ignition conversions (Dyna S, Boyer) eliminate points maintenance and are the single most popular upgrade for vintage Airhead owners.
Bing carburetor wear: The twin Bing CV carburetors on R75 models are reliable when maintained but develop wear after 40+ years. Diaphragm replacement, float valve service, and jet cleaning restore proper carburetion. Complete rebuild kits are readily available.
Drum brake maintenance (/5 and early /6): The R75/5 and early R75/6 use drum brakes front and rear. Drum shoes, springs, and cables require periodic replacement. The front disc brake option on the later /6 and standard on the /7 provides significantly improved stopping power.
Charging system limitations: The R75/5 uses a 180-watt alternator that is marginal for the stock electrical load. The /6 and /7 upgraded to 280 watts. Aftermarket alternator upgrades are available for /5 models and are recommended for riders who add modern accessories.
Pushrod tube seal leaks: Same age-related O-ring deterioration as all Airheads.
Spline maintenance (shaft drive): Essential on all Airheads. The R75's dual-shock rear end and earlier final drive design still require diligent spline lubrication to prevent expensive driveshaft damage.
Commonly replaced R75 parts
- Points, condenser, and timing advance (or electronic ignition kit)
- Bing carburetor rebuild kits
- Pushrod tube seals
- Drum brake shoes and hardware (/5, early /6)
- Clutch plate and cable
- Fork seals and steering head bearings
- Charging system (alternator, diode board)
- Exhaust headers and mufflers
- Cables (throttle, clutch, speedometer, tachometer)
Frequently asked questions
Q: Can I upgrade my R75 to a larger displacement (R90 or R100)?
If your R75 has the later 99mm engine case openings (1976+ /7 series and some late /6 production), you can install R90 (898cc) or R100 (980cc) cylinders and pistons for a displacement increase. Earlier R75/5 and most R75/6 cases have the smaller 97mm openings that limit maximum cylinder size. The crankshaft (70.6mm stroke) is shared across all displacements. Carburetors and exhaust should be matched to the new displacement for optimal performance.
Q: Are R75/5, R75/6, and R75/7 parts interchangeable?
Engine internals (cylinders, pistons, crankshaft, camshaft, valves) interchange across all three R75 series. The /5 uses a 4-speed gearbox while the /6 and /7 use a 5-speed, so transmissions do not interchange between the /5 and later models. The /5 has unique bodywork (toaster tank) and different electrics. The /6 and /7 share most chassis, bodywork, and electrical components.
Q: Do vintage R75 Airhead parts fit Oilhead or Hexhead BMWs?
No. Airhead (1969-1996), Oilhead (1993-2005), and Hexhead (2004-2009) are completely different engine designs. They share only the basic boxer twin layout and shaft drive concept. No engine, frame, or chassis parts interchange across these engine generations. Each requires generation-specific parts sourcing.
Inspected by Powersports Technicians • Only One in Stock • Ships Fast from Florida
