Friday, 30 December 2016
Terror and Trembling on a BMW R100/7
Having crashed two Jap bikes in a ridiculously short period of time, much to the editor’s amusement, I was seriously considering rescinding my previous declaration of no further interest in British bikes by buying a Trident, of all things, when these desperate manoeuvres were brought to a halt by the sudden offer of a 1978 BMW R100/7.
It was what the editor would term a perfect buy. One elderly owner, 33500 miles and a mere six hundred notes. It even came with Krauser panniers and a spare lid, the owner having decided at 75 that it was a little safer to take up knitting, or something, than risk life and limb amidst Rambo inspired auto drivers.
After the ﬁrst 50 mile ride to my squat in Shit City I was inclined to agree with him. BMW have long blurred the reality of their machinery with an image of quality and exclusivity. Having merely spent a few miles on the things in the past, I was no great expert but had absorbed the stories of great treks across the world on purring twins. What you have to remember is that the pilots are either highly experienced enthusiasts, slightly mad or just drive so slowly that a Raleigh Runabout could cope.
Having come from the terrors of an old Honda CB750, the BMW felt at first quite reassuring. Save for the way the motor shook like a Turkish belly dancer in the throes of a terminal alcohol and speed cocktail abuse and a gearchange that had all the subtlety of the editor attempting to remove a recalcitrant, chewed up engine screw, the thing burbled along quite nicely up to 60mph.
Some idiot decided to throw his Fiesta in front of my path, slamming on all the brakes and trying to hustle my way down the gearbox had the BMW bouncing and buckling in a way that recalled my youthful attempts to ride a pushbike down the steep steps of a railway foot bridge.
Suspension travel at both ends was excessive and damping had the kind of force that owners of CD175s would know only too well. It soon became apparent that the R100 needed lots of pre-planning to avoid any handling nastiness. There was little I could do about the weave that set in as 95mph came up on a piece of very smooth and straight motorway. I just sat there recalling the times I’d seen the way the back wheel of BMWs used to jump about when I’d been behind one in times past. Very reassuring.
In Shit City trafﬁc it was a real pain. The ﬁrst time I did the usual 40mph overtaking act between two lines of stalled tin boxes, dismissing the poor, misguided souls who were almost tearing their hair out in frustration, I forgot all about the two pots sticking out on each side of the bike and almost tore the side off a Volvo.
I was going back to have another try when I recalled that BMW cylinder heads were rather expensive items and Volvos made from disturbingly thick metal. I became almost as frustrated as some car owners because there were spaces where the BMW couldn’t go, that even a fat old bruiser like a CB750 could manage.
At town speeds the engine shook and the gearchange was, er, difﬁcult. Mismatch the revs with road speed by the smallest amount and the whole heap would leap off the ground like some irate old maid who’d had her bum pinched. The handlebar position hurts the wrists and the clutch is heavy enough to encourage clutchless changes, an event that produces such a frightening lurch and graunching noise that I’ll guarantee that you’d only try it once.
It made the nervous gearchange of the Honda 750 and its driveline slack look positively sophisticated. At least the BMW was easy to chuck about, thanks to a combination of relatively low mass and low centre of gravity. It was possible to sit on the BMW, feet up, right up until the thing came to a standstill. This is just as well because the seat height is ridiculously high for a motorcycle with such a lowly slung engine, another effect, I suppose, of the long suspension travel.
I quickly clocked up 500 miles running about the country in the usual horrible weather, ﬁnding that I hardly noticed the low speed tremors from the motor and could even change gear with something approaching the skill of a man with two broken legs who had just taken up motorcycling.
Unfortunately, I could not so easily ignore the machinations of high speed handling. I could push the BMW up to an indicated 115mph, which knowing the accuracy of teutonic engineering is probably a fairly true indication of top speed. At these kinds of speed it weaves like a Triumph T110 at 75mph, which to those too young to have missed such an unfortunate experience means it’ll need a car’s width of road and if you suffer from sea sickness means it’ll amuse you as much as reading Motorcycle International.
The frightening habit of a T110 to suddenly stop weaving and go into the kind of speed wobble that makes motorcycling as exciting as jumping out of aircraft without a parachute, was not quite so common on the BMW but, sadly, not entirely absent. What usually happens is that the thing would hit a bump in the road, shake its head a little and then settle down again occasionally it would decide to start oscillating instead of dying out, when shutting off the throttle and slamming on the brakes was quite an effective way of avoiding ending up target practice for NHS student doctors.
In the 3500 miles I did on the R100 a speed wobble turned up three times, which as it was thrashed ﬂat out whenever possible was quite good going. Better still, I didn’t actually crash it. Despite all my complaints about teutonic wobbling, the BM does have a certain feel to it, a sense of security that comes in part from the riding position (apart from in town), the centre of gravity and some measure of feedback from the tarmac. The latter deﬁes conventional comprehension as the usual use of soggy suspension normally damps out any reality of what the tyres are actually doing to the tarmac.
The BMW was especially at home on motorways and fast A roads. On the former it can be held at 90mph indefinitely, the riding position ideally laid out so that I was braced against the wind, the thing left stuck in top gear so that the dreadful gearchange could be ignored and the engine vibes reduced to a faraway thrum that was quite as pleasant as the exhaust bark. Go any faster, though, and the weaves intrude and the vibes begin to rattle the chassis.
Wide A roads are usually no problem, either. Just so long as the bike’s lined up for the curves well in advance then everything is just dandy, but the sudden need to brake or change direction upsets the bike, and depending on circumstances, could bounce it (across the road or leave the back end waggling around like it was death row time.
I talked to a few owners about these problems, but most of them looked at me as if I should be locked up for daring to suggest such idiosyncrasies in their beloved German masterpieces. If I had the time I would have tried ﬁtting some proper suspension components, with three inches off the travel and much stiffer springing. I did suggest this as a project to the editor, but he wasn‘t amused when I suggested spending £750 on some upside-down White Power front forks and mentioned something about lending me a hacksaw and some valve springs...
BMW’s shaft drive, at least in their early bikes, is quite a direct device and ampliﬁes any rider incompetence quite significantly. If you’re used to , recent Jap gearboxes when you just have to point your foot in the right direction and the change is done, you’ll be horriﬁed by the agricultural nature of the Beemer box. All those stories you ever heard about the shaft drive locking up in corners are all quite true.
The engine produces the kind of power that is well known to owners of British 650 twins with the added benefit that it can actually cruise between 70 and 90mph without falling apart and leaving a trail of engine parts in its wake. Also, unlike British twins, engine maintenance can be ignored with the same kind of impunity as the better Jap bikes.
That’s not to say that it is perfect because it ain’t, as I was to find out after 1300 miles. I was in the middle of nowhere when it happened. I looked down at my shoe to ﬁnd it covered in oil. Close examination of the engine revealed that the cylinder head gasket had blown. I could feel the air leaking out Out with the spanners, off with the cover, tighten down the nuts and a few prayers.
It was a long ride home, with the minimum of throttle and two stops to tighten up the bolts far beyond the recommended settings. I made it home eventually, more or less on one cylinder. Took the head off straight away and went to Gus Kuhns for a gasket. Had to go home for some extra money to pay for it but it went back together alright. In fact, it was all very easy with those pots sticking out like that. I noticed that the valve rockers had loads of sideways movement and the exhaust valve looked a little pitted and the bore was a little scratched and the thoughts of the cost of BMW parts made me pray that BMW engines didn’t act like British ones — where they run with all kinds of problems until you try to ﬁx one and then won‘t run again until you’ve fixed every other one.
Anyway, the bike ran well enough for the next 900 miles when a rattle started redolent of an early CX500 after it’s decided to self destruct. This was caused by the timing chain, which meant more money and more engine stripping that brought into play my years of training on the British bikes. I went wild, changing all the oil, setting up valve and ignition timing, balancing the carbs and giving the old girl a good clean. I was rewarded 500 miles later with a clutch that started to slip above 5000rpm. I bought a used one from a breaker and spent a weekend ﬁtting it.
My major complaint, re running costs, was fuel economy. Cynics would claim that BMW ﬁt such large petrol tanks because they have such appalling fuel economy; but as this same size tank was ﬁtted to earlier bikes which had much better fuel economy, this can be dismissed with the contempt it deserves. Fuel economy isn’t helped by a pair of carbs that don’t see any reason for staying in balance for more than 500 miles. Cruise the R100 at 90 mph and it’ll return just 34mpg. Going over the ton reduces that to 30mpg, whilst cruising at 70mph returns a slightly more acceptable 45mpg, a similar consumption to that when wandering about town.
I became so fed up with the poor consumption that I tore out the air ﬁlter to see what would happen. It made a lot of induction roar and seemed to go a little faster and the average fuel came out at 48mpg against 40mpg. I checked the plugs and they were not too white. The effect on the carburation was minimal, it could be a little hesitant at low revs, but the bike was usually so uncomfortable at such revs that this didn’t make much difference. After about 3000 miles bits started falling out of the silencer. The price of new silencers was even more outrageous than what the Japs try to get away with.
I found a couple of straight thru, reverse cone megaphones in my garage that had once graced a Norton Commando. After hacking off the old system these fitted on quite easily with a little help from a few cut up beer cans to match diameters of silencer and exhaust. It refused to start until I put a new air filter back in. Then the roar rattled windows and had the BMW sounding like a real motorcycle.
Low speed running was a little rough, but the thing could take off above 3000rpm with much more vigour and top speed was improved to 125mph. All the more interesting, then, that I was able to average, 55mpg with a best of 60mpg and worst of 42mpg. So much for all the witterings of BOFs who tell you noisy exhausts don’t improve performance. BMW could only meet the exhaust laws by constipating both performance and economy.
Despite these improvements I decided to sell the BMW. The nasty looks mature would-be owners gave me when I started her up were the things legends are made of, but I eventually found a fellow ex British bike owner who was appreciative of the racket and flush with cash from the sale of his T120 (he muttered something about not believing his luck and bloody mugs). So I was happy with the cash I made out of the deal but a little sad to see the BMW go.
If I’d fitted decent suspension and lowered the seat height in the process, then it would have been quite a useful. device, especially with the open exhaust; but really, a little too slow for me.