BMW R100/7
Electric start and classic credentials? Mark Holyoake reckons that a late 1970s airhead offers both of those and much more…
Electric start and classic credentials? Mark Holyoake reckons that a late 1970s airhead offers both of those and much more…
In 2018 an early R100/7 airhead arrived in my shed. Years ago, I enjoyed a R60/7 so it was like getting reacquainted with a long-lost pal. The clutch and brake levers on the R100 quite literally ‘fell to hand’ – it was like revisiting an old friend. Wearing my rose-tinted specs, I recall that the R60/7 was a fine rider’s machine, only hampered by occasional pinking. My current R100/7 has an ace up its sleeve; the extra torque from its increased capacity.
The 60bhp produced by my R100/7 may actually be more accessible than the ‘full-fat’ RS/RT variants. It’s definitely different to the sporting R90 and R100S models, the ‘futuristic’ R100RS and the excellent touring 100RT. The /7 is different – but not necessarily ‘less’ – and I’ve found it to be wonderfully smooth across a wide rev range. It provides plenty of low-down power, with oodles of torque that allows you to press ahead with a rush if so inclined. Last summer, the twin reliably loped along with grace and ease without vibration that might impair my progress.
In the past I owned a K75C triple which might’ve been somewhat be smoother than the /7, but this airhead feels lighter, and the low centre of gravity makes manoeuvring less of a top-heavy chore. Some of the /7’s inherent smoothness must come from the heavy flywheels fitted to this early, twin camchain motor, thereby avoiding low-rev stalling or jerky running.
An odd problem occurred in its early miles with me when the tachometer needle swung wildly around. I gritted my teeth and donned my
overalls to fiddle with things. After remembering to disconnect the battery, off came the front engine cover. The rev counter cable didn’t look like it had been disturbed in 40 years, but after a brew and some struggle it was extracted from its location. Motobins provided a replacement and after playing with the rubber fitting that stops it chafing on the case it was back in and on with the cover. Imagine my surprise when the waving needle steadied itself and behaved normally. I’m not sure this qualifies me as a proper mechanic, but dirty hands on the fresh kitchen towel caused some grief with Mrs H…
While the engine cover was off I ventured
to check the ignition points. This model predated the bean-can type which arrived a little later. I found no points and after looking further discovered an old Boyer ignition system. So my hoard of spare points, an automatic timing unit and condenser can reside safely on the shelf, and now I know why the ignition has proved so reliable, so far. The only issue with the Boyer is that the previous owner located the ignition unit under the seat in the tool tray, and the wires are as tight as guitar strings. It may be wise to relocate the unit to somewhere with a better airflow and less stress on the wires. There’s no kickstart on this model, it relies entirely on the electric start. That’s good news for my knee but it puts the load on the battery and Boyer instead.
No sooner had I returned to the road after fixing the tacho, than the speedo needle started waving like Her Majesty on a walk-about. Huuumph. Going back to my friendly supplier of bits-and-bobs, I obtained a replacement speedo cable. Off came the petrol tank again: thank heavens for the rubber bungs and my wing-nuts that hold it on. I was careful not to get grease on the instrument end of the cable, and followed the routing into the worm-drive near the output shaft-drive by the rider’s right ankle. It fitted, although lining up the cable abutment and the retaining bolt was a challenge. All reasonably straightforward, and once again I had two instruments relaying the information of smooth progress.
The Fenland roads which I ride are not the IoM TT circuit. But the bumps and other irregularities I always encounter are smoothed by the BMW’s front suspension; its eight or so inches of travel stop the undulation and jiggling reaching the handlebars. The five inches of suspension travel at the back provide a superior action, and both help the handling qualities over rough roads – so today’s potholed roads present no problems. My rear end is pampered by the soft but supportive saddle, which gives comfort for the long run without chaffing the occupant!
However, after settling down with the /7 for a few hundred miles, the ride seemed to become a little too saggy. It was like being on a see-saw. The original Boge rear suspension units gave up their damping and things got a little too soft – after only a 40 year stint. Tsk tsk, you’d think this would be covered by the BMW warranty! Thoughts of Öhlins replacements and Progressive springs filled my mind and I started searching. I considered a set of Nivomats – the air-assisted type that were standard on RT models. These ‘self-levelling’ units were supposed to pump themselves up. My old K75 was fitted with Nivomats and I thought they were great, but recall that they’re not rebuildable. They’re also a tad expensive for not a massive improvement in performance.
After much searching I came across a pair of slightly used OE Boge rear units. I realise these could go the same way as the originals but they were £40 for the pair with
good chrome and intact springs. The builtin adjusting handles are a boon, and save skinned knuckles too.
An invoice in the bike’s paperwork suggested that the gearbox has been overhauled at some stage in the past four decades, and it snicks between gears in a manner that surprised me. No clunks or stiffness, no snatching going up or down. It’s not a super-slick Triumph gearbox, but it certainly doesn’t suffer the traits often reported on 1960s and ’70s Beemers. This model pre-dates the remote linkage stuff, too.
The /7’s single front ATE disc used to get a poor press, but it seems to work OK. It’s not the best I’ve used but has been fine for my usual speeds. The facility to check the rear brake lining is clever, too. My machine has the unusual arrangement where the cable to the master cylinder runs under the fuel tank. Perhaps they intended to keep the master cylinder out of harm’s way? After clocking up some miles, I checked the brakes and found that this under-tank master cylinder had at some point leaked onto the frame. Mine has a 14mm master cylinder – there are oodles of different sizes so you need to be careful when ordering parts.
As spares for this set-up are becoming harder to find, I also acquired a handlebar master cylinder. Changing to a handlebarmounted master cylinder will mean a change in brake lines, but will do away with the cable twixt the bar and the under-tank unit. I might get away with the same 14mm size, although some folks prefer 12 or 13mm cylinders to raise the hydraulic pressure – but that’s with Brembo brake calipers. Before making the change I’d also need to consider the effect on the throttle cable and the switchgear. This conversion might not be as plug-n-play as it seems, so I’ve opted to stick to the original set-up for now. The bore looked good so I honed the cylinder for a new piston and repair kit, rather than opting for full surgery. The handlebar unit can wait for another day... scary stuff for a home mechanic. Still, it’s only brakes!
The carbs are slightly less intimidating. This model uses the 32mm Bing units, not the 40mm ones fitted to the RS and other variants. I noticed that sometimes after warming up the engine seemed to idle too high. With my experience of the shocks, tacho and speedo cables, I had visions of more purchasing yet more spares. But a pleasant day in the garage meant I could clean and balance the Bings. I read somewhere that it’s best not to set the tickover too low when using a Boyer ignition, so erred on the high side when re-setting the tickover and it now seems fine.
Most of the servicing / shakedown tasks were completed before winter uncurled her icy fingers. Oils and filters were changed; valve clearances checked. I fitted some new BMW fork gaiters – see, I really DO know how to mechanic! I think the driveshaft has some play on the lower coupling but the U/J looks to be in good condition, although I’m not entirely confident about such things. Airheads from this era were equipped with BMW’s oil-bath version of the shaft drive, so avoid the oft-reported gremlins of the later
Paralever type.
A wee bit of noise I’d noticed was probably down to the complete lack of oil in the driveshaft casing. The manual suggests there should be approximately 100cc, but I drained out approximately two teaspoons’ worth. I wonder if the previous owner forgot or if it’s leaked out... That may need further attention, and there’s some tinkering to be done with the fuel taps to stop a leak by on the lefthand side; a new gasket methinks.
Another frustrating issue with a bike of this particular age came to light when it was time for it to be taxed for the first time without an MoT. The info at the Post Office and DVLA was confusing, and in the process of getting it sorted the postal service or DVLA managed to lose my registration document. Not the bike’s fault of course, but worth bearing in mind on your classic’s 40th birthday.
It’s oft remarked that BMW quality dipped in more recent times, and while my /7 isn’t a /2 it does have a ring of solidity – the same solidity I found on the K75 but without quite so many modern computer-controlled components and fuel injection. The /7 feels like it was designed by motorcyclists for motorcyclists, rather than being accountantdesigned. Airheads from this era avoid many of the later ‘improvements’ – for instance it still has wire wheels, which were re-spoked some time in my machine’s history. These
are more aesthetically pleasing to me than the problematic cast wheels which replaced them, and which had to be replaced under a recall if I remember rightly.
Fortunately for me, this particular /7 hasn’t succumbed to a café racer conversion. Apart from the Boyer ignition, it’s reasonably standard. For a 40 year-old bike it hasn’t been too troublesome – in our time together I’ve discovered a series of foibles which needed fettling but nothing too dramatic or beyond my mechanical ability to resolve.
Twisty, undulating country roads really suit the /7’s riding style. Now that the suspension’s sorted, the bike rises and falls along with the road with the torquey engine delivering a lovely, stimulating experience. The handling isn’t up there with your average Ducati but it offers no hinges or nasty unexpected behaviour to catch you out. Plus the large petrol tank allows you to pick and choose your fuel stops; no panic and a longer riding range than many motorcycles. Oh, and it makes that unmistakable BMW sound: sweet, distinctive music; not at all raucous but a rich and elegant tone to enjoy.
Overall, I’m very pleased I grabbed one when it happened along. A few people find them dull and uninspiring, but my R100/7 achieves what most of the new retro-styled bikes set out to do – have a classic look with modern handling. It’s one of the most understated, well-thought-out classic motorcycles I’ve ever had the pleasure of riding. The R100/7 operates just like a modern motorcycle, while still giving a taste of the rich history of BMW and its boxer engine. Spares availability seems pretty good, although some parts can be pricey. You could easily argue that the R100/7 was, for its time, an outstanding long-distance partner. Really, it’s still true today. Four decades later, it’s still a great ride.