BMW K100 – The new go to Bike for Custom Cafe Racer Builders

BMW K100
"K100 @ Sciencepark Amsterdam" by Marcel Oosterwijk is licensed under CC BY-SA 2.0

Last Updated on 13/04/2021

The BMW K100, aka as the Flying Brick, is making a comeback as the go to bike for Cafe Racer custom builders. There’s more to this great Sports Tourer though and it deserves to be remembered for the ground breaking 1980s motorcycle it was.

The K100 was the German marquees first shot at creating a ‘modern’ bike to shake off the ever-growing feeling that they were becoming a stagnant manufacturer known for their reliable but ever ageing boxer engine powered motorcycles.

It wasn’t a bad direction for BMW to take and with a team of designers ready to develop a bike to back the modern concept, the K100 was born. Let’s get into the detail of how it came to be.

History of the BMW K100

By the 1970’s the likes of Suzuki, Kawasaki and Honda were flooding the market with their Japanese wonders – reliable, fast, relatively maintenance free and affordable. 

Buyers in Europe and the U.S were spoiled for choice but BMW weren’t ready to just roll over and pack it all in. After all, they were one of the leading motorcycle manufacturers in the world. 

They also knew they couldn’t beat their Japanese counterparts at their own game and so to justify their heavier price points, they needed to offer something different, and worth a buyers investment. 

The boxer engine with lineage back to the 1920’s was due for retirement. Increasing pressure from EU emissions regulations was leading to designers and engineers hitting a brick wall with ways to work with the engine to meet the requirements. 

Scrapping the air-cooled staple wasn’t an easy decision but a necessary one. The predicament however, was how to exceed the expectations the boxer would leave in its legacy. 

It was a man named Josef Fritzenwenger who finally came up with the concept that could change the game for BMW. A longitudinal four-cylinder liquid-cooled engine mounted with the engine on its side, not dissimilar to the Indian’s of the 1920’s with key difference being the engine laying on it’s side. 

The engine would have a low centre of gravity thanks to its mounting position and a straight line drive train, aswell as the inherent stability and smoothness that four cylinders provide. 

The liquid-cooling is the advancement that really stepped the new design up from the air-cooled predecessors and the four-cylinder engine was the most technically advanced for the time.

The engine and transmission was to be kept accessible for easy maintenance and the bike was built for meeting high mileages that BMW was to become known for. No detail was overlooked on the engine development for the K100 as it was the focal point that was going to drag BMW into modern motorcycling. 

After it’s release in 1983, the nickmame of ‘Brick’ or ‘Flying Brick’ was soon adopted for the BMW K100. While it may have lacked the aggressive, intense concentration the Japanese bikes needed, the K100 was built to be smooth, have excellent range, plenty of ‘oomph’ and provide a pleasurable riding experience.

It returned 90hp powered by its 987cc engine and a real world top speed of 135mph. 

BMW had combined fuel-injection, aerodynamic fairings and shaft drive into one realiable bike, something that other machines had one or two features of but not all three in such a well built package. 

The K100 remained in production until 1992 and saw several model variants produced over its lifespan including the K100C, K100RS, K100RT, K100LT and K100TIC.

The differences were mainly changes to fairings and touring accessories as well as the K100TIC model which was developed for use by the Police, Fire and Ambulance services as well as other authorities.

BMW K100 Performance

The BMW K100 wasn’t met with the rapturous excitement that BMW had desired but it was a slow burn and eventually both press and public came to warm to the latest BMW bike.

The early K100 models were not without issues which with any model – especially with a whole new engine design – could be expected. Despite the engine design the bike felt top heavy, putting off some riders and the bike suffered vibration and overheating problems. 

Channeling air into the radiators wasn’t an issue but the K100 struggled to let it back out again away from the engine bay, this would cause for a very hot rider. These and other issues were addressed over the models lifespan.

In the early 80’s the K100’s release was a a landmark for the world of sports touring and this would be followed up in 1989 with the K1.

The BMW K100 was built for practical, long-distance riding and every detail was thought through; the various trim levels and accessory kits from BMW is what eventually started to win over the public. 

Today the BMW K100 is becoming a popular choice for custom builders with many turning the bike into a cafe racer affair by stripping the machine back to its core and removing the fairings. 

Buying a BMW K100

BMW K100 given the cafe racer treatment
The BMW K100 is fast becoming the donor bike of choice within the Cafe Racer scene

The K100 has seen a recent resurgence within the custom world with both pro and shed builders deciding that it makes a great donor for a custom build project and it is fast becoming the donor bike of choice for those planning to build a Cafe Racer.

It has become such a popular donor that custom shops are now making bolt on replacement parts for those working on their own K100 Cafe Racer project.

These completed custom K100’s are swapping hands for big cash. Car and Classic has a very nice custom ‘Flat track’ inspired K100 advertised which would set you back £14,991. This seems a little steep given a standard K100 price should be between £1,500 – £5,500 (condition dependant).

In the U.S you should expect to pay up to $6,000 for a standard K100.

When looking to buy try and find a K100 that is still rode regularly rather than one that’s been used as a dust collector for the last few years, they don’t like to sit still for long periods. Don’t be put off by high mileage either, the K100 was built to chase down the miles.

Here is what you should look out for when thinking about buying a BMW K100:

  • Knocking noises from the engine on start up, the early models had six rivets that could work loose and this causes the shaft to rattle
  • Check for worn/leaking oil and waterpump seals – this can lead to a whole host of issues
  • The rear main seal for the engine should be checked for oil leaking – it can cause the clutch to slip as oil gets into the clutch housing
  • Make sure the ABS system is in working order, it can be a very costly fix and sometimes exceed the value of the bike itself
  • Check the state of the centre stand for rust and wear/tear. It is an overlooked problem that the centre stand fails and the bike collapses due to deterioration.

Restoring a K100

With the BMW K100 lending itself to custom builders it means that parts are pretty readily available for the bike, whether they be original or replica parts, it is unlikely that you would struggle to find what you need. 

If you add to that the fact a BMW K100 project bike doesn’t need to set you back a fortune to begin with, you could be on to a reasonably priced restoration project. 

On that note however, one thing to remember is that some things on the K100 (and other K series BMW’s) are very costly to repair or replace. 

Make sure that the high ticket features are in working order and don’t require much work to avoid any surprise costs that will shoot up the overall cost of your project.

This is particularly important if your intention is to sell the bike at the end of the completed restoration; standard K100’s are not selling for a fortune, it is the custom bikes that are seeing the most high end pricetags on the market. 

James Sherlock is a pretty good source for parts in the U.K and there are a handful of reputable BMW specialists in the UK and U.S who will be able to source what you need and give you advice along the way. 

There’s also a thriving forum for K100 owners with a busy buy and sell or swap section. Find the forum here.

To give you an idea of parts prices here are some examples off eBay:

  • $60 – Stainless Steel Screw Kit
  • $130 – Exaust Collector Manifold 4-1
  • $75.45 – Ignition Coils
  • $299.00 – Gas Tank
  • $49.99 – Air Intake Box

Is a BMW K100 a Good Investment?

The BMW K100’s value is in getting one and riding it. The bike offers a comfortable sports tourer package that will give people plenty to talk about when you pull up at your local biker spot and if looked after will likely outlive your riding years.

While a landmark BMW design, it is not a bike that will suddenly become a coveted classic like many of the air-cooled boxer engine BMW’s. 

With that said, you won’t lose money either so you could buy one, enjoy it, and sell it for for what you paid if you needed to make room for something new.

What might change the game for the K100 is if the custom world keeps the momentum of using the K100 as a base bike for cool builds. In this case they will get harder to find and more expensive. Therefore, an unmolested K100 in a few years time may well be worth a pretty penny. There are many variables with this though so it’s hard to say for sure. 

Alternatively if you have a budding custom builder inside you, getting your hands on a BMW K100 and turning it into something unique, wouldn’t necessarily set you back a fortune and nicely done custom K100’s are selling well on the market. 

Verdict

The K100 was BMW’s first step into the new world of modern motorcycles and they did it oh so well. Was it as sleek and elegant as what was available from Kawasaki etc? Probably not. 

However, the craftsmanship, design, technical advancements and quality of the K100 is where its strength lay and it is also where BMW’s strengths lay as a whole. The K Series is what moved BMW forward and proved they had what it takes to compete in the global market.

About Emily 36 Articles
Emily is passionate about motorcycles and when she isn't writing for us she is a freelance artist doing mainly commission based work illustrating motorcycles.

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