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Bike Review - Posted 8th November 2013
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BMW R100RS - Monolever

Richard Crompton clocked up 75,000 miles on his airhead Boxer in the 1990s. These days, he's kinda pining after another one...

Back in about 1990, I bought myself a present of a three-year-old monolever R100RS from my local franchised BMW dealer. Not the usual choice for a 23 year old. My bike had slightly less than 3000 miles on the clock and had been registered to a local coach company. The BMW dealer stated that the bike was the pride and joy of the company's owner and was used purely as a high days and holidays toy. The bike looked as good as the day it left BMW's factory and was resplendent in its white pearlescent paint.

Power to weight ration improved by using line drawing... BMW R100RS Monolever

BMW had tried to ditch the Boxers in 1983 when they launched the flying bricks, but they soon found that for a lot of BMW fans the machine had to have no more than two pots arranged to keep the rider's feet and ankles warm and dry. BMW relaunched the monolever Boxers in 1985 to cater for those BMW faithful who weren't obeying the orders to love the new-fangled machines.

The monolever engines produced less power than the older twin-shock models, and I heard a whisper that the powers that be considered the monolevers to be all-new models and so they had to meet tighter emission tests than the twin-shock editions. To ensure that they passed these tests the engines were de-tuned. I don't know the truth of that, but I do know that riding my R100RS was like being propelled by a steam engine - whatever engine speed was showing on the tacho in whatever gear, easing the throttle open felt like being pushed forward by a giant hand in the small of the back. The wider you opened the taps the stronger the shove, and the quicker you opened it the fiercer the shove was.

I was leaning on a lampost... BMW R100RS Monolever

Shortly after buying my R100RS, I noticed that there was an oil weep around the cylinder head gasket on both pots. Taking the bike back to the dealer I was advised that a boxer BMW was only really considered run in at about 10,000 to 15,000 miles. This was a real surprise to me as all the bikes I had owned up to that point were usually in need of an engine rebuild at around those sorts of distances. The dealer changed the cylinder head gaskets FOC for me and I have to say that I was less greedy with the throttle until the bike had done 10,000 miles. The engine was noticeably sweeter after about 10,000 miles than it had been when I had bought the bike.

I rode about 12,000 'purely pleasure' miles per year in the time I owned the BMW. I soon became aware that the bike was capable of a lot more than I was asking of it, and that it was a lot more capable than anything else I had ridden. Certainly the rider's lack of talent embarrassed the bike, rather than the other way round.

After the first summer's use I found that the bike was rock solid cranked over to the point that the fairing lowers would drag on the deck, although with practice I managed to find how to place my feet on the pegs so that my boot soles would scuff just before the fairing and thus I could work out how much further I felt happy to lean it over. Before anyone thinks I was riding like a nutter I would like to say two things…

Firstly if I had wanted to ride like a nutter, then an R100RS would not have been the natural choice. Secondly, I had attended the local constabulary's Better Biking course (the fore-runner to BikeSafe), and was preparing to take my IAM motorcycle test. The R100RS really did reward riding to the police 'system' of motorcycle control - it would go round corners on rails if you entered the corner on the correct line, at the correct speed and gradually accelerated through the corner. The bike would get very upset and unsteady if you had misread the corner and tried braking or violently changing the bike's line.


Physically the Boxer was far more comfortable than the appearance of its riding position would have you believe. 500 mile days were no problem, and in fact on two separate occasions I rode from Aberdeen to Gloucester stopping only for fuel, necessary breaks and a meal. After arriving at home after 800-plus miles and 14 hours on the road I felt that I could have pushed on for another couple of hours riding as I had 'got into the zone'.

My first big adventure on the BMW was to the 1991 TT, and this led to my first real issue with the bike. After a couple of days on the island the BMW would not pull above 3500rpm. The ability to rev out gradually got worse until the bike was unrideable, so a call to one of the famous breakdown services ensued. Embarrassingly the mechanic admitted defeat after about an hour of messing about. The bike was still unrideable so was towed to the Island's BMW dealer. They were diamonds, and two days later the bike was as fit as a fiddle - it turned out that the carb's emulsion tubes were blocked. At that point I decided I had better get more acquainted with the workings of the Boxer - I had been happy to work on my other bikes, but had fought shy of working on the BM. I found that routine servicing was well within my abilities.

I reckon I put about 75,000 miles on the BMW before I got rid of it in 1996. I would have kept it longer but for the intervention of a young car driver who was awarded six penalty points for (lack of) driving ability. It was touch and go whether the BMW would be rebuilt, or scrapped by the car driver's insurance company (I was TPF&T covered). It was rebuilt - and the dealer who got the work told me that the insurance assessor had authorised the repair because he could see that the bike had been well loved and cared for prior to the crash. Initially I was pleased to get the BMW back, but after a while I realised the bike just wasn't the same for me, so it was sold.

In my time away from BMs I have owned a variety of other bikes and Dad has bought a 1983 R100RT. He wanted one ever since BMW launched the model. On a touring trip around Scotland shortly after Dad bought his R100RT it started to struggle to rev out. It got steadily worse to the point the bike was unrideable, and I thought to myself… this rings a bell. Sure enough, we took off the Bing carbs and found that the emulsion tubes were full of rubbish.

I can't say that my BMW was without fault. The carbs would go out of balance as the next service got closer, but twenty or so minutes with the vacuum gauges would have the engine running as sweet as a nut.

Also my bike was very sensitive to the condition of its HT leads. The genuine BMW HT leads seemed to have a depressingly short service life, bearing in mind how expensive they are. After going through two sets I decided that using solid copper HT lead with weather proof NGK resistive caps was the way forward. I did not have a misfire once I stopped using the genuine leads.

Airhead BMWs on

It has been interesting comparing Dad's slightly older BMW with mine, as there are a few things which BMW sorted out for the monolever bikes. For example, Dad's bike originally had the fuses in the headlight shell with a right rat's nest of wires - this was not the easiest to work on in when a fuse blew on a pitch black rainy night in the middle of Scotland, 30 miles from the evening's accommodation. My bike had the fuses under the saddle - much better.

His bike also has the rear disc brake which can be a pig to bleed properly. When Dad got his bike he asked me to help him service it (which was like Einstein asking a first-form school pupil to explain the theory of relativity to him). We put braided hoses on the bike and bled the front brakes in no time. When it came to the rear brake I threw the towel in with disgust as it just would not pump up. I went home for a beer or two, but the following day found that Dad had somehow managed to get the brake bled on his own without my hindrance.

Perfect balance: No centrestand needed...

17 years motorcycling on a variety of non-BMW machines, all of which I have loved but none quite as much as the R100RS, has led me to the conclusion that I need to return to the Boxer BMW fold…

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