BMW R-series Airheads 19691996
Affordable and easy to work on the R-series was BMW’S move into modern bike building. Bike’s Dealer goes retro…
SPANNING 25 YEARS and over 35 models, BMW’S R-series heralded the German marques’ arrival into modern motorcycling thanks to brilliant innovation and a modular concept philosophy. Powered by an evolution of BMW’S traditional air-cooled 4v boxer motor, the new Type 247-engined bikes boasted more performance and reliability. Airheads have always had a cult following, but these days interest in the models has peaked thanks to renewed interest from custom builders. Parts interchangeability across the years and models is extremely high, meaning owners of earlier R series bikes can benefit from the innovations of later models, and there’s also a very strong aftermarket parts supply. They’re also extremely simple for home mechanics to work on, too. Pick up a basket case for as little as £1000.
KNOW YOUR AIRHEADS
The basic model run down goes like this: /5 19691973 in 500cc, 600cc and 750cc; /6 19731976 in 600cc, 750cc and 900cc, R90S is the most desirable; /7 19761980 500cc, 600cc, 750cc, 800cc and 1000cc. For ’81-’84 BMW dropped the slash symbol and these are known as the ‘Brembo brake models’ (due to their Brembo braking systems). R80G/S is the most desirable.
Despite being noisy, particularly on /5 models, the valve train is reliable if well maintained. BMW recommend checking clearances every 8500 miles, but it’s worth checking them at 5000 miles. The top cover gasket can be reused if intact.
aluminiumironAll models internal alloyup boreto barrels1981 sleeve. featuredwith Latera cast model cylinders were upgraded to full aluminium barrels with a nikasil plated bore, which were lighter and had better cooling and wear properties. This means later and larger bores fit earlier bikes, for example many R75/7 owners fit R80 barrels. However, care needs to be taken to match the cylinders to the cases, and also take into account squish bands, piston ring type…
‘They don’t make them like they used to’ and in terms of BMW bikes I’d agree. We sell loads of modern stuff and the build quality is nowhere near the standard of this older stuff. I bought a 1976 R75/6 from a chap who had it from new. He said it was nearly three times the cost of the Honda equivalent at the time, so they were expensive even then.
Pre-1985 bikes were designed to run on leaded petrol and so were prone to valve seat wear problems when run on unleaded fuel which manifested itself in excessive tightening of exhaust valve clearances. BMW introduced new seats made from an upgraded material for later models, and these can be retro fitted into the early model cylinder heads. There are also very good aftermarket valve seats to buy.
The original ‘bean can’ pointstype ignition system fitted to pre-1981 twins can mean poor starting and unreliable running. However, there are lots of aftermarket alternatives including the option to upgrade to an electronic ignition, which BMW introduced on 1981 onwards models.
If a high-quality semi-synthetic 20/50w oil is used you should be looking at changing oil every 5000 miles, then replacing the oil filter and its O-rings every other service with a genuine BMW item. When it comes to choosing an oil, look out for an additive called ZDDP in the ingredients list, as this compound helps protect camshafts.
It’s normal for an airhead’s gearbox to rattle at tickover, especially when warm, but this noise should disappear when the clutch is pulled in or the engine revs are raised slightly. That said gearboxes are notoriously poor and prone to failure, so regular maintenance is vital. Early /5 models came with a four-speed gearbox, and bikes from 1974 onwards came with five-speed ’boxes. Pre-1981 five-speed transmissions often suffered with broken dogs resulting in a loss of fourth gear. Bikes built between ’85-’94 also suffered excessive wear on the output shaft bearing due to BMW omitting a circlip and groove
from the shaft itself. This was reinstated on late models.
Shifting on early /5s can be enhanced by fitting later model parts such as Teflon-lined clutch cables, rose-jointed gearshift linkages, the post-’82 shift detent kit and the lightest possible flywheel/clutch carrier. BMW also recommend inspecting and lubing the input shaft splines every 10,000 miles, as dust generated from the dry clutch can cause the shaft to dry out and grind the splines away.
All airheads from 1969 onwards featured an electric start, which was backed up with a kickstart. However, the kickstart mechanism on /5 five-speed ’boxes is renowned as being very weak and relying on it to start the bike can result in transmission problems.
TUBELESS SPOKED WHEELS
Cross-laced wheels were introduced on the 1988 R100 GS, allow the use of tubeless tyres, and are still used by BMW today. These wheels are very strong but need specialist care if damaged, as they are extremely difficult to true. Wheel builders such as Hagon (hagon-shocks.co.uk) offer a rebuilding service for cross-laced wheels.