K1100SX Project Is Finally Here!

Our BMW K1100SX has been tested and is finally ready. We have articles about all of the various modifications, setups, and settings. In them, we'd like to tell you about the process and what we encountered along the way. It took us longer than we expected, but better late than never!

We've tried to create a minimalistic, classic, last-century motorcycle which would be both functional and comfortable.

Chassis

We were lucky to find spoked tubeless wheels from a GS model that were in excellent condition. This predetermined the design and the overall concept of the project. We knew we had a chance to make something unique, as there currently are no similar motorbikes. The wheels were put onto the original factory components, so the entire setup works reliably.

The original shock absorber was replaced with an adjustable YSS. The standard fork had to be shortened due to the installation of a larger front wheel. Test rides showed that the springs should be changed because of the large weight reduction, or adjustable fork cartridges installed, which would make the suspension more modern and functional.

New triple clamps were installed with a smaller offset, resulting in a better response to countersteering and maneuverability, especially when leaned over. Meanwhile, the rake angle of the bike stayed the same, which will continue to provide good stability.

Electronics

Standard analogue electronics are heavy and bulky, so we elected to incorporate Motogadget digital components. This resulted in an overall weight reduction of 12 kg, a cleaner design with an "empty" engine, and no need for a battery, control panel or relay. Everything works well (not scared of water, vibration or mud) and provides a unique look for similar projects.

Brakes

We changed the front brake master cylinder to a fully adjustable modern ABM with an integrated reservoir, making it easy to brake using only two fingers. Similarly, the rear brake master cylinder was replaced with a compact ABM, which fits nicely into the minimalist concept of the bike.

Handling

The overall setup is fully adjustable. ABM 3D clip-ons are the best on the market, as they allow for any handlebar configuration. The foot pegs are mounted using the LSL 2-slide model, for which we had to make a bracket with adjustable guides. It was fairly easy to set everything up after having taken only a few rides.

Engine

There were no big modifications to the engine. The K1100LT comes standard with short gears (we will install a final drive from the R1200CL with a lower ratio) and enough power. We removed the crankcase ventilation system with oil catcher and airbox, which saved us some weight and reduced soot in the cylinders. The OEM exhaust was replaced with a lighter REMUS system with an aluminum canister. We decided not to shorten the exhaust as this could cause flat spots when pulling away and opening the throttle, and such a setup would also need tuning.

Weight

The bike is comparable in weight, size, and power to a modern urban motorcycle at 210 kg with a full tank and all liquids.

We paid special attention to weight, because a decrease here would improve a lot: controllability, fuel consumption, dynamic characteristics.

During operation we realized that it was possible to remove the radiator fan and the corresponding relay. Since there is nothing behind the radiator, air is continuously blowing through and the engine does not heat up. This can save us a couple of kilograms. We tested the bike in tight traffic at low speed on the hottest summer day in Moscow, and the fan turned on only once, after standing still for a while.

Cost

Cost strongly depends on OEM parts (motorcycle, GS wheels, final gear with cover and rear caliper from GS model). Aftermarket parts on our bike cost about 5,500 EUR, but this sum can be reduced by installing cheaper master cylinders, handlebar and controls.

We would like to thank Imperia for the provided shooting spot!