Dähne-framed Daily Rider from Kradhaus Bikes…
Born in 1944, Helmut Dähne is a BMW motorcycle racing legend. As a teenager, he went to work for BMW Motorrad as a mechanic and later went to German tire brand Metzeler, working with race teams at circuits around Europe and beyond. But he’s best known for his racing exploits.
While he was too tall for GP racing (~6’3″), Dähne was a force on production-based machines from the 1970s-90s, racing at long circuits like the Nürburgring Nordschleife and Isle of Man Snaefell Mountain Course, usually wearing his signature red and white leathers.
Few other riders can say they rode their own racebike to the Isle of Man…especially from as far away as Germany!
“He was one of the most popular heroes to race in the Isle of Man Production TT in the Seventies and his name is synonymous with BMW motorsport. The lanky German rider won his army of fans because he was a true enthusiast who prepared his own bike, rode it all the way from Munich to the Island, raced it over the Mountain, and then rode it home again.” –Motorcyclist
Dähne also helped develop a frame specially-designed for racing, powered by a highly-modified 750cc R75 air-cooled boxer engine. In 1972, he won the legendary Imola 200 on such a racer, and in 1976, he finally won a TT, racing in the 10-lap 1000cc production class on a modified R90S…using a cylinder head he borrowed from a spectator’s bike after breaking an exhaust valve in practice!
What’s more, a similar frame was used by the Butler & Smith team that campaigned the R90S in the first year of AMA Superbike.
Enter our new friend Christoph Reintsch of Germany’s Kradhaus Bikes — a man whose motorcycling heritage runs back to his great-grandfather, who was riding an Indian around his native Bohemia in the years before World War II. Today, Christoph works in the shop with his father and even sometimes his grandfather, and he’s recently begun building his own frames, employing the time-honored designs of past racers like Ferdi Kaczor and Helmut Dähne.
Last month, we featured the “Kaczor” R60/7 built for Kradhaus’s media and marketing manager, Marlene Mößbauer. That bike used the frame design of Ferdinand “Ferdi” Kaczor — a BMW engineer, racing legend, and contemporary of Dähne’s.
At the same time, Christoph built the Dähne frame that underpins this scrambler. Whereas the Kaczor frame and attendant suspension were ideal for Marlene’s petite stature, this Dähne-framed build was set up for Christoph’s taller proportions, using Kawasaki Zephyr 750 forks and Ikon rear shocks.
“The idea was to generate a suitable ‘everyday vehicle’ for my size with good performance and chassis / technology. With the supermoto past, the style direction of the bike was clear. Optionally, the bike can be changed to street tires.”
While the engine cover may read “R75/6,” it’s actually a 1065cc with high-compression pistons, lightened internals, Dell’Orto carbs, and a 2:1 Hattech exhaust system. The air-cooled boxer engine now makes a stout 80 hp and 92 Nm (68 lb-ft) of torque.
The result is a unique daily rider perfect for Christoph’s stature, with solid power, upgraded brakes, and plenty of flat-twin grunt. Below, we talk to Christoph for the full details on the build.
BMW Scrambler: In the Builder’s Words…
This was our first project with a self-modified frame. This and the Kaczor frame were built in parallel. Due to my height, this frame was used for the Scrambler conversion. The length to the rear upper shock mounts and the longer shocks / fork result in a higher seating position.
The idea was to generate a suitable “everyday vehicle” for my size with good performance and chassis / technology. With the supermoto past, the style direction of the bike was clear. Optionally, the bike can be changed to street tires. As with the other projects, a clean look is very important to me.
The engine with big bore kit was self-built and further optimized. The use of the old air filter housing and the hood with “R75/6” lettering provides a well-behaved look. Final carburetor tunings are now running with the help of a lambda tester to ensure the best possible tuning over the entire range.
Build Sheet / Specs
Power: approx. 80 hp (57kW) at 6330 /min, torque 92 Nm at 4900 /min
Engine:
- Four-stroke two-cylinder boxer engine, air-cooled
- Engine case R100R, Big Bore Kit
- Asymmetrical camshaft, bore x stroke 98.0 x 70.6 mm
- Displacement 1065cc, compression 10.5:1
- Double ignition, type silent rush
- Cylinder heads, type R100, modified
- Piston and connecting rod lightened
- Valve train lightened, lighter valve adjustment screws
- Two Dellorto PHM carburetor Ø38mm, intake type /7
- Facilitated single-disc dry clutch
- 2-into-1 Hattech complete system “OYK”
- Five-speed gearbox type /7
Chassis:
- Frame: Series /7 modified according to Dähne / Butler & Smith racing design
- Front fork: Kawasaki Zephyr 750, shortened with progressive fork springs, Ø41mm
- Triple clamps: K75S
- Rear swingarm: type /7
- Shocks: IKON Type 7610
- Front 19 inch spoke wheel, rear 18 inch spoke wheel
- Front tires 100/90-19, rear 120/90-18, type Heidenau K60
- Aluminum wheel covers,
- Front double disc brake Ø 300mm, rear drum brake Ø200mm
- Tank: Moto Guzzi Le Mans II with integrated speedometer
Time required:
September 2020 until June 2021
Approx. 800 h
Follow the Builder
KRADHAUS – Bavarian Custom Bikes
Christoph Reintsch
Media and marketing: Marlene Mößbauer
Web: www.kradhaus.de
Instagram: @kradhaus_bikes
Facebook: Kradhaus Bikes
That exhaust system is so cheesy! Definitely needs a redesign by Yoshimura!