Buyers' Guides

Sunday, 6 June 2021

BMW R100S

Whilst the UMG has already featured the BMW boxer twin in previous issues, I wanted to write my own report having been an owner from new and I think the sort of person who appreciates the twin for what it is. I would guess that many people who pick up this magazine are going back to bikes for the second time, perhaps having a grown up family and a bit more time and cash available - someone who having been brought up on British twins won't be able to adjust to a motor that starts to give its best at 6000rpm.

I had a Honda CB550 and even did 50000 miles on it but never did get used to the need to rev the balls off it - it never felt like a bike should, anyway. A BMW feels like a bike ought, it’s got some soul and in many ways is similar to a British twin except that bits don’t fall off and it doesn’t break down. By the same token, anyone brought up on LC Yams needn't bother reading on. One ride around the block on a BM should be sufficient to put you off. I suppose the best way to tell if you are a potential boxer fan is to imagine you’ve just bought the latest MCN, where there’s a road test of something that interests you do you look at the top speed and standing quarter times to two decimal places? Then forget the boxer, it ain’t for you. If, on the other hand, you check out the mpg and fuel tank range, then read on.

My first advice to anyone who has set his heart on a twin is be patient. Be prepared to spend some time looking around. There are a lot available and occasionally a real bargain comes along. Remember that a lot of twins are owned by what we might call mature gentlemen and I have seen examples offered that were ten years old with as little as 3000 miles on the clock at quite sensible prices. A good source of used BMWs is the owners club magazine. Its worth joining just to gain access to this. Each month there are some 25 or so bikes for sale.


Don’t be put off by high mileage examples. In reasonably careful or rather respectful hands a BM will go around the clock, so at thirty or forty thousand there should be lots of life left in the beast. My own boxer has chalked up not far short of 100000 miles and is still going strong. I don’t propose to offer a blow by blow account of its life history - simply its good and bad points and what a might expect from a similar machine.

The bike is a 1978 BMW R100S, bought new in, er, 1981. I found it in the back of a large Kent dealer with bits missing. They had obviously given up hope of selling it, having registered it the previous March to beat the car tax (remember that one, it broke a few dealers, you know). I bought it for £500 less than the list price and on reflection it was a great buy. My first impression was to wonder what I’d let myself in for. What was all the fuss about? Riding home it felt rough and shook like mad if I opened it up below 2500rpm. It was certainly no faster than the CB550 and every time I took a modest left hander the side stand hit the tarmac.

I can understand how people have bought BMWs thinking them the ultimate and then quickly sold them in a fit of disillusionment. BMW ownership, though, creeps up on you and you find that while it does nothing exceptionally well by the same token nothing is really bad either - it’s all a compromise.

Let’s start with performance. Nobody buys a twin for outright performance. A good Jap 500 will piss on even the 1000 BMW twins, certainly on acceleration, and the later hyperbikes on top end as well. My wife’s XBR (hardly a hyperbike) has no problem chasing my twin.

On the old, heavy flywheel models any attempts at rapid acceleration away from the lights will soon be thwarted by changing up into second it won’t have it, not until that hefty flywheel has slowed down, unless you mercilessly kick the gear in regardless. Where the performance does count is the bike’s cruising ability. It’s just so relaxing. Even at the ton the motor is just burbling along at 5000rpm - if you can stand the induction roar it will cruise like this for hour after hour without wearing you out.

Best speed for me is 85mph, but I have a Windjammer on mine and that induction roar is amplified inside the fairing - a problem shared with the RT. The FJ1200 I’ve also acquired (temporarily) needs much higher revs to go the same speed and is more difficult. to live with on long journeys - I end up driving the FJ slower than the BM despite its vastly more powerful engine. In town, for instance, the loping gait of the twin lets you believe you're travelling much slower than you really are - I’ve often found myself rolling along at twice the limit, quite obliviously whereas the FJ creates the impression of speed.

The twin scores on fuel too. Nominal consumption is around 50mpg, like my old 550. But on the CB, at very high speeds, that would drop to the low 30s. This coupled with a small tank meant it was quicker in the long run to travel at 60mph. At speed the BM drinks a little more, but only down into the forties, which still gives a 200 mile range. I’ve found it’s necessary to fiddle with the needle jets and replace them and the needles ever so often to maintain good fuel economy. Some owners are plagued with carb balance problems, but I’ve usually left well alone with no noticeable problems.

A problem I had for some time was the bike’s insistence on slopping petrol over my feet due to sticking float needles. I finally cured the problem by fitting an in-line fuel filter - £2 at B&Q or £5 at Gus Kuhn. My second piece of advice is to get to know some owners before spending out on parts. Some BMW parts are ludicrously expensive. Take carb diaphragms, genuine BMW £14 each, exactly the same at your local car accessory store, 69p.


If you don’t know you can overspend on all sorts of things. Clutches, for instance - I use my BMW for commuting 22 miles of dual carriageway and then 8 miles of London traffic. It probably explains why I can get 10000 from a back tyre and why I’m on my fourth clutch. The first went at 20000 miles and was repaired by a dealer at the cost of £90, the second I did myself, using a Borg and Beck replacement that lasts longer and costs only £25. Most jobs on the bike are straightforward, the clutch is the exception needing the hire of a special tool to extract it.

Servicing is simple enough, however, and it’s important to keep everything in tip-top condition, particularly as the days get colder. The first really cold morning when there’s a frost will catch you out. If the motor isn’t in spot-on tune and the battery isn’t absolutely 100% you’ve had it. I’m on my fourth battery in six years again the unwary owner might be persuaded to purchase the genuine BMW item at close to £60. With a little imagination and a file to remove some unnecessary ribbing from the battery, an Exide RE2 from Big M or B&Q does the job better for £35.

Clutch wear is not typical and on the smaller twins is almost unknown. The battery, however, is a BMW bogey as is the next item - the stands. The BMW centre stand has been a bone of contention since the 5 series was introduced in the early seventies, yet nothing was done to improve it. The stand pivots on two short bolts which fasten onto threaded lugs in the frame. Continual use loosens the bolts until the stand gives way and the bike falls over. Diligent owners tighten them up at frequent intervals, but eventually the threads in the frame cry enough - if you’re lucky they haven't already been tapped out to the next size up.

If they have then you have big problems because the remedy then is to replace them with Allen bolts and to fit them is an engine out job. I fixed mine by drilling a hole through the lug and bolt and stuck in a split pin - simple but effective. The design of the stand itself is sound - allowing both wheels to clear the ground for cleaning or wheel removal but does not permit one to ride off - it has to be kicked back into position.

The prop stand is useless. It’s impossible to put down unless you're seven feet tall. What’s more the bike must be tilted away from you to put the stand down, not much fun if it’s heavily loaded. Once down, it leaves the bike over at a few degrees, precariously waiting for a gust of wind or a nudge to knock it over. If you are really lucky, a one time bike owner will decide to move your beloved beast a few inches to park his car when the stand will fling back - I’ve heard of bikes dropped and the perpetrator has promptly buggered off.

I threw mine away and bought a Bob Porecha special - a snip at £38. There’s only two other bad points and one that’s not really the BMW’s fault. It concerns rear wheel removal easy on a stock bike, but as most are fitted with Krauser case frames, getting the back wheel out is a fight to say the least. Frankly, it’s such a hassle that I get my tyres replaced for me - fine until you get a flat tyre.

The other point is the rear brake. If possible buy one with a drum. The rear disc brake works fine for a while but the position of the master cylinder is such that it is being showered whenever there is a bit of water on the road. Eventually, it fills up with crap and stops working. BMW recommend fitting a new master cylinder at £80 - and this is an annual problem. More adventurous owners strip and clean ’em out - if they are lucky it'll work for a week or two. Even at its best you can stand on the rear brake lever without fear of locking the back wheel.

Now, those are all the nasty bits, the good bits more than compensate. Its outstanding feature is the quality of finish. I have more than on one occasion used it for a whole year, including winter riding, without giving it a wash - when I’ve eventually got around to it the paint has come up like new - I can say with hand on heart there is no rust whatsoever on it. I sometimes see a fine smattering of rust on the chrome but this disappears with a little elbow grease and polish. Even in places where I’ve knocked the frame when removing the gearbox the paint has chipped to reveal a nice thick green primer. I had an ’82 RT for a short period and the finish on that was nowhere near as good. I think there was a strike at the undercoat factory for a couple of years because my mate’s 1981 RT is a rust heap.


The exhaust system on used machines will almost certainly have been replaced, many machines have stainless steel systems fitted which if they are not so pretty do last a long time. Reliability of my twin has been remarkable. It has only ever failed me once at home when it refused to start in cold. weather. Last summer I took off around Europe with my wife on her own bike, doing no more than checking the oil and tyre pressures for a 3000 mile trip when you have 90000 miles on the clock and can do the same, then you can say your bike is reliable.

I haven’t yet mentioned the essential character of BMW riding. It wasn’t long after buying it that it evolved its own name - Sylvester. Partly because it was silver and because Sylvester is my favourite cartoon cat. At about 70,000 miles: I was faced with spending about £300 and it seemed a good idea to consider chopping it in for something new. The £300 included new tyres, suspension and a top end overhaul - I'd read too many stories of valve heads snapping off at 50k on the 7 series to ignore the possibility.

Anyway, I was going to trade Sylvester in for a K100 Pichler, the dealer offering £1200 for the R100. Just before I did the deal I found he would give £600 off the list price for a straight cash buy and. was going to break my twin if I did part ex it as they didn’t think anyone would buy a bike with 70000 on the clock.

I bought the suspension units that afternoon and a day later fitted new tyres. Decision made! A year later I came across a spotless RT at a good price. After I spent a week cleaning up the older bike, in order to sell it, the bike looked so good that I decided to sell the RT instead. I decided that if I could get the BMW up to 100000 miles I could write off its cost and ignore my self imposed rule to run only one bike at a time, which is how I came to buy the FJ1200. Well, that’s going too, but I now know what will join my lovely BMW.
Something which has escaped mention in these pages but which has more character than anything else I’ve tried - a perfect complement to what most would consider a boring old man's bike yes, a Harley 883.

A few tips to look for when choosing a BM. From front to back: Spin the front wheel gently. If the owner has used a high pressure hose on it, the bearings could well be shot and can be heard. Next, have a close look at the fork legs. If the stanchions are pitted expect interminable fork seal problems. I have little experience regarding knocks and rattles in the motor - mine has always knocked and rattled anyway but you need to see if it will run on each cylinder, one at a time. If it won’t, it may not be too serious a problem, but may mean it needs a re-bore - if it’s 1981 on that means a new barrel. Next, look under the seat, it’s prone to rust and costs lotsa cash to replace. Prior to the test ride check that it can be rolled on and off the centre stand if it can’t, accept no excuses because it’s an expensive repair and warrants a hefty discount.


Don’t be afraid on the test ride to ride it flat out. Ideally, give it a thrash up a long steep hill so that any weakness in the clutch will show itself. All the usual rules for buying used applies - the character of the owner is just as important as the condition of the machine. Finally, if the vendor says, I’ve only had it a few weeks and it’s the most underpowered, overrated heap I’ve ridden; my GPz would have run rings around it; it shook my false teeth out and it weaves like a bat in anything over a Force 2 breeze; what’s more it takes over 200 yards to shift gears up or down and the back brake’s as useless as men’s tits - buy It - if you’re over 40 chances are you'll love it.

Eddie Barnes