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Bike Review - Posted 9th February 2015
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Post-war BMW Twins

In 1950, BMW returned to building twin-cylinder motorcycles. Talana Gamah takes us on a whistlestop tour of the marque's classic airhead models, produced over the following three decades...

Post-war BMW Twins

Post war twin-cylinder BMW production re-started with the 500cc R51/2: an updated pre-war design with plunger frame and tele forks, a format that including the R51/3, various R67 workhorse types and the sport R68 formed the basis of the range until 1955. Then Earles forks and a new swinging arm frame sought to modernise things, although the engines followed previous form: a simple, low oil pressure ball / roller bearing flat-twin pushrod type which then enjoyed the incremental evolution that was to become a BMW trademark.

Post-war BMW Twins

Equally simple 6V electrics (not a fuse in sight) and magneto ignition take care of the sparks department. A four-speed gearbox and the fuss-free shaft drive made the ultimate tourer. Well made, reliable, and costly to buy in a time of declining sales, these expensive machines almost finished off BMW. The R50/2 and R60/2 are probably the most relaxed and easily sourced. R69 and R69s will cost a premium.

All look similar to the casual observer and only an examination of the engine and frame number will confirm which model is which in some cases. So this provides a chance to impress the inexpert without bottomless pockets if you like that sort of thing.

Post-war BMW Twins

What you do get is a comfortable long distance ride, with good brakes, between 24 and 42 horses depending on the model, and a host of well thought out details. Failing magneto coils cause bad starting when warm, and cast brake drums crack with age, but spares are readily available from specialist suppliers, or online auctions for the financially challenged.

Post-war BMW Twins
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From 1969 the twins use a redesigned frame with bolted on subframe, and tele forks return as standard. The new 500/600/750cc engines are a high oil pressure, plain bearing, one-piece crank incarnation, with the cam under the crank and driven by a duplex chain. Alternator 12 volt electrics, coil ignition, and an electric starter that is standard on all but the smallest model.

Gearbox remains four-speed with kickstarter. Drum brakes all round, and the one-size-fits-all ignition key in the top of the headlamp make it through to the /5 series, a reminder of things past. A new combined speedo/ tacho instrument is only found on these machines, so can be scarce or expensive to replace.

Post-war BMW Twins

SWB (short wheel base) frames gave way to a LWB (long wheel base) update in order to overcome handling foibles. BMW even introduced plastic, chrome, and colours other than black; the colours survived, the chrome did not!

Picking up a truly original example is getting more difficult, and expensive, if only because many parts are interchangeable between the /5,/6,and /7 series. The /6 revamp gave us five gears disc brakes on all but the smallest, a larger headlamp with a proper ignition lock in the side, and a conventional speedo/tacho layout. It also lopped the 500cc from the bottom of the range, and gave us the R90s. Even the maker of dependable tourers saw the need for a superbike, a mantle taken over by the R100RS with the advent of the /7 series. Power ranged from 40 to 70 horses across the different models, larger tanks all round, squared off rocker covers, and cast wheels that eventually replaced the spoked type on all but the fleet contract or police bikes.

1981 saw a major revamp with light flywheel, electronic ignition, better brakes and upgraded forks. The 600 had been lost on the way as the smaller R45/65 had taken the role of entry models a couple of years previously. The Hans Muth styled R65LS further extended the choice for buyers of smaller BMWs.

The R80G/S started a fashion that no one would have predicted. This original G/S was supposed to replace the standard R80, but it didn’t work out quite that way.

Post-war BMW Twins

BMW were now looking to the K100 as the future but public demand saw the twins linger on until the monolever incarnation. The engines softened, peak power now down to 60hp, finish had deteriorated and handling improved. The disc brake that had been fashionably installed astern on the larger capacity machines was finally replaced with a drum.

The final R80/100 developments were unfaired restyled paralever types that borrowed heavily from GS experience. Spokes, and rounded rocker covers returned as the airhead range looked back on the eve of its demise at the hands of creeping EU regulations. Earlier bikes will generally cost you more.

Rotten seat bases, and tanks that rust around the fuel tap are some of the most common problems. Engines can snap crankshafts (uncommon), leak oil around the pushrod tubes, or wear valve guides at higher mileages. Carbs sometimes dump fuel all over your feet, the paralever R100GS had a reputation for eating shaft joints, and the gearbox can be a weakness, though specialist suppliers offer exchange services that can be a better option than trying a rebuild yourself.

Post-war BMW Twins

Bikes seem either to fall into the ‘very high mileage’ or ‘pampered, under-used toy’ category. More recently a passion for modifying can see you paying a lot more for a bike with no front mudguard and a bandaged exhaust…


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