BMW Motorcycle Tech

I will update this page from time to time with things I have done in the past, ideas I am working on,

I am trying to work out a way to get my new sidecar rig to go backwards under its own power, rather than having to get off and push it backwards using my rickety knees...

Below is a scan of a brochure that I received from Wolfgang Kayser of Germany. He is one, if not THE, preeminent BMW motorcycle gearbox builders in Europe. He also offers inside-the-box reverse gear options for many models of BMW motorcycle transmissions. Unfortunately, they have not completed development of the R1200 reverse gear modifications yet as of my last contact with them earlier this year. (Jan/Feb 2009)

I have a "home-brewed" trail reduction bracket that I designed for reducing the steering trail on my new sidecar rig. Here are a couple of layout drawings that I did while designing it, and some photos of it during installation. I also added a collar on the front spring/shock assembly to add extra preload to the front spring to help maintain proper ride height.

The trail reduction bracket made a quite noticeable improvement in steering effort on the R1200RT/Hannigan-LT sidecar rig! I can do basic lane changes and mild sweepers with just two fingers on one hand grip now. It was definitely worth the time/investment!

After a little bit of riding with the reduced trail, I decided that I did not like the hydraulic steering damper attached at the lower fork sliders as supplied by Hannigan. So I designed my own friction steering damper unit that mounts between the handlebars up at the top for easy adjustment by the rider. It is lightweight, simple, and does not impart any "bump steer" into the front end like the old damper unit did. I think it is a keeper!

R1200RT "Dark Side" rear wheel conversion (suitable for solo or sidecar duty):

As this motorcycle came to me with a busted rear wheel, and was destined for sidecar duty, I decided to go ahead and do a car-tire/wheel conversion on the rear axle right away. It turned out that I rode the bike for several months before having the sidecar installed, including a several thousand mile trip out West to Denver, up into Wyoming, and then back home through the Black Hills and Badlands. The automotive rear tire worked just fine the whole time, even when leaning it over a fair amount in some of the curves.

I had an adapter plate machined, and then had it and the aluminum wheel anodized to protect them from the elements. Anodizing is a chemical process that alters the top layer of molecules of the metal, making the coating permanently bonded to the base metal. It is much more durable than powder coating.

For sidecar duty, a car-tire conversion is nearly a must-have for the larger bikes. They simply eat up rear tires otherwise...

Just some stuff related to work I am doing with my sidecars. Comparing power outputs, power-to-weight ratios, gearing changes, etc...

Seeing and being seen are VERY important to your safety on a motorcycle. Since the introduction of the /6 models in 1974 BMW has been noted for the excellent headlights installed on these bikes. But they can be better!

The E-code halogen headlamps used by BMW do an excellent job of putting light on the ground and out in front of the bike without blinding oncoming traffic. But the wiring to the headlamp bulbs is undersized for the job. All headlamp current actually has to flow all the way out to the dimmer switch on the handlebar, and back into the headlight shell in smaller diameter wires than what they should be for the wattage of the headlamp bulbs. This causes extra resistance in the lighting circuit, which cuts light output at the bulb.

The solution to this problem is the installation of relays with shorter & heavier gauge wiring to direct power to the headlamp bulb. This reduces resistance losses in the wiring to a minimum, providing maximum output at the bulb.

There are several people out there selling pre-fabricated wiring harnesses for doing this which include instructions and all the necessary parts. Or if you are the least bit handy with a wire stripper and soldering iron, you can make your own for much less, and with a much higher level of personal satisfaction. And, it is much easier to snake a wire through a harness/strap/grommet if you don't have the connectors crimped/soldered on yet....

Protecting against rodents: Many motorcycle owners take their bikes out in the spring only to find that a resourceful rodent had set up housekeeping in the air cleaner housing during the winter. I happen to have a year-round small rodent issue where I live. What I have resorted to is using 1/4" grid soldered hardware cloth over the intakes on all of my infernal combustion engines around here. It is readily available, inexpensive, easy to work with, and does not corrode with the heavy tin-solder coating used to assemble it.

The basic version of this guard is to just cut a piece about an inch larger than your inlet and fold the extra over the sides. I use heavy plastic wire ties (zip ties) to hold it tightly in place.

On my Beemers; to preserve the hopeful/potential/designed-for "standing wave" at the inlets of my /7-later snorkels, I formed it into a box that stands away from the inlets to not disturb flow right at the ends. Have no idea if it makes a difference doing that rather than having it flush against, but it can't hurt. And if a leaf gets sucked against part of it, there is still airflow around the rest of the "cage".

Here are a couple of photos of what I have installed on the snorkels of my 1995 R100RT:

Bleeding brakes had always seemed like a real hassle. You traditionally need a helper to pump the brake lever/pedal while you open the bleed valve and watch for bubbles. At the same time one of your needs to be watching to make sure there is enough fluid in the reservoir so that you don't suck any air back into the system. For single-man bleeding, they sell vacuum bleeders for brake systems, but I don't like the risk of drawing air in if the reservoir goes dry while you are down by the caliper.

For BIG money, they also sell pressure bleeding systems which feed fresh fluid in under pressure to force the air and old fluid out. One obvious advantage is that it will not let air enter the system from loose fittings or from a small on-vehicle reservoir becoming empty during bleeding. The downside can be the possibility of more mess from fluid under pressure, and of course, cost for the equipment.

I came up with a simple and effective and LOW COST pressure brake bleeding system for use at home. It can be used for bleeding either from the top-down or bottom-up. It is easily controllable for flow rate. It can be easily used by a single person. And it offers less mess or chance of spillage than some other systems.

The basic element for my system is an inexpensive pressure sprayer from the hardware store with a built-in pressurization pump and a trigger control for control of the sprayer. To that I add appropriate fittings to allow connection of a length of clear tubing. At the other end of the tubing I attach a modified top to fit the brake reservoir needing to be bled. The modified top has a fitting to allow fluid to enter through it while attached to the reservoir, and a gasket to block any air venting into the reservoir. It may also be helpful to have a short length of tubing projecting downward from the inside of the cap to be able to easily maintain/adjust fluid level inside of the reservoir.

When the modified cap is installed, squeezing the trigger on the pressurized tank forces fluid through the tubing and into the reservoir. When the bleed valve is opened at one of the wheel cylinders/calipers the pressure in the system forces fluid out into your waste catch container. Any fluid bled is immediately replaced by the fluid being fed from the pressure tank, so there is no risk of the system running dry. By having a long enough tube, you can be at the wheel with the pressure tank, triggering flow, while you open and close the bleeder screw/valve.

Here are a few photos of the unit I have assembled for my Airhead BMWs. I also have caps for other vehicles that I have owned or helped maintain. As you can see in the last photo, I cut my own gasket from an old motorcycle inner tube to seal the cap when mounted, and for extra insurance sealed the vent slots in the inner flange using a hot knife to melt the plastic back across the openings.

02/22/10