A burger and fries is a great meal once in a while, but you wouldn’t want to make a steady diet of it. BMW riders in the late 1970s were getting tired of the same old menu—air-cooled boxer twin, modest power, dowdy looks—at about the same time as Japanese manufacturers were offering up some pretty tasty in-line fours that were smoother, faster and cheaper than anything from BMW. So the chefs in Bavaria gathered in the kitchen and whipped up a real treat—a liquid-cooled four, laid on its side and clothed in swoopy bodywork—that still tastes good today, and borders on becoming a modern classic as well.
The K100RS threw BMW orthodoxy out the window with its liquid-cooled 987cc four, but toed the company line with a longitudinal crankshaft that aligned with the driveshaft to reduce the power losses typical in drivetrain layouts with several 90-degree changes of direction. With the head on the left and the crankcase on the right, routine maintenance like adjusting the valves was simplified.
The “brick” engine was fed by Bosch LE-Jetronic fuel injection in place of the carburetors that had fueled generations of boxers, and two valves per cylinder were deemed appropriate to the bike’s sport-touring mission; in all, about 90 horsepower were available at a full twist of the throttle. The shaft drive got a new moniker, too––Compact Drive System.
It took a while for roundel fans to embrace the K100RS. The bike felt top-heavy despite the low engine layout, and vibration plagued early models, as did engine heat; while good at letting cooling air into the radiator, the bike was less efficient at channeling it out of the engine bay, and the rider paid the price. The styling, too, was a bit too avant-garde for those who preferred the less flamboyant boxer. The heat issues were resolved on later models, and the K100RS model’s solid sport-touring performance, optional hard cases and sporty seating position soon won over not just the doubtful BMW faithful but others who found nothing as attractive in other brands’ lineups.
Contrary to what you might think, the best used K100RS is one that’s been ridden a lot. Examples that have sat idly for years get grumpy when they’re awakened, and develop issues that need immediate, and often expensive, attention. Check the weep hole under the front of the engine for signs of oil or coolant, and the one in the rear of the engine case for oil that indicates the rear main seal or forward transmission seal has died in its sleep. Watch out for lateral movement of the rear wheel, notchy steering-head bearings and poor fueling, and ask if the splines in the drivetrain were lubed on schedule.
Prices are still reasonable—between $2,500 and $3,500—and don’t shy away from high-mileage bikes if they come with complete service records. The K100RS is one of the best budget-sport tourers out there, and a good bet to appreciate over the years.
1985-1992 BMW K100RS
The Good:
A landmark sport tourer with a healthy dash of style and the potential to become a practical classic.
The Bad:
Vibration and heat plague early models. Awesome power and acceleration were not on the options list.
Specs
Displacement: 987cc
Final drive: Shaft
Wet Weight: 536 pounds
Fuel Capacity: 5.8 gallons
Seat Height: 32 inches
Wow, this brings back some very sweet memories, I’ve owned and ridden 21 different motorcycled, (brands/styles/etc.) in over 40 years of riding and to this day my favorite machine was a 1987 K100RS BMW! Just a sweetheart of a motorcycle, 100 mph all day, loaded for 2-up touring or just sporting around! 🙂 You can keep the new Super PIG looking K1600GT, not anywhere near as good looking as the K100RS, jmho, ymmv. ! My favorite trip was a full West Coast tour up Highway one, the Pacific Coast Highway! 🙂
Boosted my 1985 K100rs in 1988.Rear shock with stronger dual dampening helped handle the jump to 148 RWH (actual dyno result). 90,000 miles under boost with a total of 117,000 miles on the odometer and it needs a motor freshening. Rings, valve grinding, a light pass to flatten the head and a new set of more modern spray injectors are planned for 2018.
Comfort and reliability abound
Turbo?? I’m lQQking at a 1986 with hard bags and a largish upper ferring and swoopy windshield!
After years of riding old British iron I’m still growing to love my ’92 K100rs. It’s a heavy beast, and a chore to handle on a tight road. But, it accelerates like a monster and will do the ton all day. Kinda reminds me of my old Trident, same bore and stroke, same power delivery, just heavier.
If it shifted on the right side it’d be perfect.
85 RS here in North Carolina. Plenty of twisting back roads and elevation changes makes this old classic a very nice change from my 71 HD chopper.60,000 miles and still very reliable!! Just love it.
I owned a 1991 model shortly in 2003. It had an accessory sweat that I had reshaped. Ultimately, I sold it due to an oil pump issue. Great handling and smooth running bike
Did the ‘97 Ironbutt Rally with a 1986 K100RS; with sidecar. Bike performed flawlessly.
I’ve a 91 BMW K100 RS with 132 000 on the clock spline work done at 100 000 head rebiult at 100000 even though compression was perfect.
Very little vibration.
I think I’ll wrap the clock up alot more going through Alberta rookies before I am too old to ride.
I have a 1986 Motorsport special edition RS owned from new. It has been a life defining machine after 46000 miles slowly spread across Europe over the decades. Although still immaculate, now withdrawn from front line use being replaced with a new R1200RS – and only because the brakes are from another century. It makes friends everywhere it’s parked and most definitely BMW got it right first time. Magnificent.
Hi Steve, I have one that I am having re-painted. Is there a ‘M’ logo on the tail-piece (halfway between the BMW roundel and the Motorsport pinstripes and RS badge)? Have found one pic that does not have it, but my bike has a very faded M logo in that position? Thanks! Manie (Pretoria, South Africa)
Hi there, K100 RS 16 v
.Original bikes just had the RS chrome letters on the rear seat shroud.
I have a 1990 model RS 16 v, used for touring, mainly ex communist block countries., what a machine.cruise all day at warp factor speeds if needed.. I have original sales brochure.
I’ve 132 000 miles not kms, miles.
I brought the bike up from Arizona in 2009.
It’s solid as f**k and has been spline lubbed and valve train work as prescribed ….still can hit 149 MPH
Course it’s brief I’m chicken and Alberta Canada roads offer plenty of wildlife and cops!
I have an 85 K100rs. Upgraded the front forks by drilling out the effects of the dampening rods and installing .90kgm springs with race-Teck’s gold valve emulators. Replaced the rear shock with an upgraded rebuildable and tuneable shock. What a difference, holds a line under throttle in the turns even through the bumps! Awesome machine. Watch out for the ECM cable connection, I have added a couple of zip ties for security. No other issues, amazing bike!!!
My first ‘proper’ bike was a 1987 K100RS I bought with 13,000 miles on the clock in 1989 solely to get me to the IoM TT. It was the Style edition in all black with a grey saddle. I quickly bonded with that machine and covered many blissful miles. Kids came along and so the bike was sold – a decision I regret to this day.
I’ve had 2 more ’87 K100RS’s since but am now on a 1990 16v. It was white/silver but I had it resprayed in my favourite black. If I’m honest compared to my main bike (2017 R1200RS SE Sport) it handles like a barge, but it brings back memories of the long balmy summers of my youth and for this reason I’ll never part with it.
Wonderful real world riders machines.
I made the mistake of buying one of these in 1985. Without doubt the worst bike I have ever owned and possibly the worst I’ve ever ridden. Compared to other bikes it handled like two pogo sticks linked together with a piece of string. I don’t recall a journey when the rear wheel went via the same route as the front wheel. The engine vibrated like nothing else I’ve ever ridden. I’ve ridden twins and singles that, although they vibrated, were nothing like as unpleasant. And as for the fuel injection system, it spent more time spraying me with petrol than supply the engine. The build quality was appalling. Just the tought of it’s first winter approaching saw most components showing signs of serious corrosion and the instrument panel used to fog up to such a degree it was near useless. The paint finish was poor as well. All problems I had never experienced to such a degree on all my previous bikes and certainly haven’t experienced since. As for the seat it was seriously uncomfortable. Maybe I was just unlucky and had a “Friday Afternoon” bike but all in all it put me off anything BMW for life. I know BMWs get pretty good write-ups these days but I just can’t bring myself to commit to one after that experience. I went back to Japanese after that RS and have stayed with them ever since, something I have never regretted, especially my new Wing.
Wow, sounds a lot like my time owning a Ducati. I ride a Concours but have always been intrigued by the 4 valve K100RS. Your experience makes me question that interest.
Had an ‘89 K100RS SE, a ‘91 K100RS 16v, and a 92 K1. My favorite to ride was the ‘89. Felt much lighter and had better torque. Still have the K1 but it is serving as garage art unfortunately. They did not Handel very well, were slow to rev, as if they had a huge flywheel, and overall felt heavy as a result. This was great for 1200 mile days at triple digits but not canyon carving.
Great reading throughout. Im a 63 year old returning to the joy of motorcycles after a 30+ year break. Fate would have it that a year ago a buddy sent home a m/c magazine with my wife and the front cover inferred a review of the latest BMW Touring m/c. I glanced at it a few times and finally read it. Then I checked Craigslist for used motorcycles for sale. 20 minutes earlier some dude had posted his 1985 Collector Plated K100RT for sale with 29,000 klms on the clock. Friggin Spotless and the price was $3500 Canadian. I bought it and picked it up the next day. Took some pictures and applied for the new Collector Plate. 2 weeks later I was on the road. Parked it for the winter and in march of this year pulled it out and changed all the fluids and gave it a new set of Dunlops. She’s 37 years old, looks magnificent and motors down the road beautifully. Sure the front forks are too springy … so that’s on the list for this winter and the seat puts my 230lbs and 6 foot frame too far forward but that too can be modified. Rubbish on washboard gravel roads but sure puts a big grin on my face as we haul ass down country roads or cruise at strong tripple digits on open highway. No Oil Leaks, impressive acceleration, triple discs and all day stamina. Who knew that a middle aged 63 year old could fall for a classis 37 year old … and together they enjoy heading for the hills. Oh yeah I’m looking for advice on those springy forks and I should probably search for a flat seat.
I had one as used bike in 1986. horrible to drive in traffic and hotter that hell riding it. Twins only for me.
Just found a 1986 burgundy with black hard saddlebags, 26,000 miles! 450 miles on new tire’s, unknown maintenance history! $3000.00 ANY good?…from Wyoming USA 🇺🇸 👋🤠
Like ANY True Classic M/C company Beemers are not for everyone; However, if you ride rice you think there nice , but when you finally bury your internet habit and try Schnapps you know there Tops! Own 7 Beemers; ride each on for a different reason, love country roads and when you got to get there quick the R1200RS comes out to do battle, one really sweet ride. K76S is a great fun machine, R1200LT is Unmatched for miles ridden in absolute comfort.