• Kai

BMW K100 RS Caferacer project

Updated: Apr 21, 2020

Hi everyone,

In this blog I'll show you how to give a whole new life to an old motorcycle that deserve to be taken care of, and probably save it from ending in a junkyard. How? By turning it into a Cafe Racer!

Let´s start from the beginning.

The donour bike is a 1985 K100 RS in perfect state. When I picked it up it only had 29.000km on the clock.

Step one. Disassemble all body parts. I bet the bike already lost 25 kilograms by just removing all that stuff.

The result after day one.

After the speedo is gone and the first cut was made on the tail 😱 it’s now time digging into the lines. It’s very important understanding how the current lines find or don’t find themselves so I get a better understanding where I need to adopt/ changing them to achieve my vision of how the bike shall look in future. The yellow lines (tank) will need finding the red ones (frame) going forward one or the other way.

The BEP 3.0 had initially been developed for those who were looking to replace the original cockpit (also labeled „Brotbox“ in German-> “Lunch Box”) of their K75, K100, K1000 or K1 bike with a speedo of a third-party manufacturer. And everything done completely stress-free without soldering and tangled wires. No alterations to the wiring harness or modifications of the vehicle are required. Simply plug in and off you go!, fully universal   interface fits to all connectors ! (round/square)

First test after replacing the speedo with BEP 3.0

Work in progess...

Day one on my fork mockup for the K100. The Original front wheel carries a telescopic fork with 41.3 mm standpipe diameter, which is a big disadvantage compared to a fork with 41.0 diameter. You simply don´t get cool clamps in 41.3.

I decided swapping against a R100 R fork. Et voila, the 43.0mm stub handlebars fit. 🤓

And so we are starting the fork adoption from BMW R100 R.

Weekend so let´s swap the fork.Two different fork manufactures are used on BMW K models: Showa with an outer upper tube diameter of 1.612 in (40.9 mm) and Fichtel and Sachs measuring 1.627 in (41.3 mm). The new Showa is already waiting in the background.

Mock-up done!

That is how a K100 tank looks from the inside.

Schrott or not? I am going to sell the used break discs and go for new ones. There´s however maybe still some pocket money in it for me if the discs diameter is not below 3.6mm. The tool addict I am my collection also contains a micrometer. The discs still have some good 4.1mm left.

Over one kilo of solid BSK Speedworks exhaust, beautiful sound and quality.

The mounted exhaust is coming along great!

I´m waiting for the weekend ahead to continue working on the bike.

Reorganised my workshop the other day. The K now is on the ramp. I’m now waiting for my tail since 2 months...

From a 3D PC design to reality. The rear mudguard was printed with ABS plus. ABS plus is much more robust against heat and impacts as you would expect it for a fender and the extra strut in the middle even improves torsional strength. There´s however a small challenge when it comes to proper mounting at the bike.

The original plan was using two mount points right over the swing arm at the gear box. Just it turned out that a) after removing the spring nuts there´s no threads in the holes and b) the fender would sit too close towards the wheel and swing arm. See picture below.

Time for plan B. A complete new mount using exiting threads from the battery holder. Made from stainless steel, the new mount accomplishes a high quality look, increases overall stabilty and moves the guard away from the wheel and swing arm.

Job done!

Some rim porn for you.