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.
We were lucky to find spoked, tubeless, wheels from an existing 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 obsorber was replaced with a adjustable YSS. The standard fork had to be shortened due to the installation of a larger front wheel. Test drives indicated that springs should be changed, because of great weight reduction, or adjustable progressive fork cartidges 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, particularly on slopes. Meanwhile, the rake angle of the bike stayed the same, which will continue to provide good stability.
Standard analogue electronics are heavy and bulky, so we elected to incorporate Motogadget digital components. This resulted in an overall weigh reduction of 12kg, a more pure 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.
We changed the front brake master cylinder to a fully adjustable modern Spiegler with an integrated brake box, making it easy to brake using only two fingers. Similarly, the rear brake master cylinder was replaced with a compact Spiegler, which fits nicely into the minimalist concept of the bike.
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 I needed to construct a supporting bracket with adjustable guides to make work. It was fairly easy to set everything up after having taken only a few rides.
There were no big modifications to the engine. The KL1100LT comes standard with short gears (we will install final gear from R1200CL with less 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 lead to some problems with the start and throttle opening.
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 were particularly confused with the weight, because a decrease here would improve a lot: controllability, consumption, dynamic characteristics.
During operation we realized that it was possible to remove the radiator fan and the corresponsing relay. Since there is nothing behind the radiator, air is continuously blowing through and the engine does not heat up. This saved us a couple kilograms.
Cost strongly depends on OEM parts (motorycle, GS wheels, final gear with cover and rear caliper from GS model). Aftermarket parts on our bike cost about 5500eur, but this sum can be reduced, if installing cheaper master cylinders, handlebar and controls.