Evolution Cycles
1087 Hickory Hill Pkwy.
Hubertus, WI 53033
414-573-7031
Upgrades for the beloved "Airhead" BMW motorcycles:
I will update this page from time to time with things I have done in the past, ideas I am working on,
or some "Gee, wouldn't it be neat if..." ideas that I have rattling around...
Electrical:
Ok, one area where many people seem to find fault with these bikes is the charging system. The stock charging system was not designed to handle lots of extra accessories, lights, heated clothing, etc. SO, what can you do? There are several exotic (spell that expensive) upgrades that you can do to REALLY boost your electrical output, and most of them even retain the stock appearance and basic operation of the motorcycle. The very radical have gone so far as to mount an automotive alternator external to the motor with a drive pulley on the crankshaft and holes/slots cut in the front engine cover for the drive belt. Less radical, but not much less expensive are two competing upgraded output charging systems which are a complete "plug-n-play" replacement for the stock system. One uses the same basic design of components, just beefed up, the other uses a brushless alternator and solid-state regulator/rectifier unit. People have reported good success with both systems.
Personally, I LOVE the EnDuraLast brushless high-output charging system that I installed on my winter sidecar rig. BUT - For those with shallower pockets/bank accounts, there ARE some things that you can do to your stock charging system to improve the performance noticeably.
TUNE UP/IMPROVE STOCK CHARGING SYSTEM:
STEP 1: Proper grounding of the battery, chassis, engine.
[photo of ground straps here]
STEP 2: Ensure good sound wiring/connections at/to/from the positive battery terminal.
[discuss]
STEP 3: Ensure good clean & sound connections at all points in the charging circuit.
[discuss]
STEP 4: Upgrade connections & wires to/from Diode board. Ground wire. Charging current. AC current from Stator.
The single largest improvement that I noticed is when I upgraded the connections at the diode board. I started out by observing that the stock wiring to/from the diode board had hardened over time, indicating to me that it was overheating from attempting to carry more current than it should. I then observed that rather than good solid bolted connections for these wires, the diode board relies upon blade type terminals for all connections other than grounding. If you look at a BMW diode board, you will see that it is basically two buss bars connected by the rectifier diodes and a connector board to hold everything together. The upper buss bar is the negative terminal bar, and the lower is the positive terminal bar. There are two holes in each of these buss bars which I utilize to create a solid bolted connection to the diode board for the charging current flowing out of it towards the battery.
In the first photo below you can see the basic modification done on a stock diode board. I have taken two M6 hex head bolts and managed to snake them into one of the holes in each buss bar and secured them with a jam nut on the backside. CAUTION: Being a positive terminal, you must be careful to restrict the length of the lower bolt so that there is adequate clearance between it and the timing case when the diode board is mounted in the engine!!!
The second photo shows the two wiring harnesses fabricated for installation. The single wire cable goes from the lower {positive} bolt to the solenoid on the starter, which is connected directly to the positive terminal of the battery through a heavy cable {as shown in third photo). The double ended cable is used to provide positive grounding of the diode board and front case of the engine. One terminal connects to the block at the front starter support bolt as shown in the fourth photo, and the other to the front case at a convenient point, or to the stator frame as shown in the fifth photo. I also fabricate heavier gage wires for carrying the AC current from the stator to the connectors on the diode board. The heavier wiring throughout this area and more solid connections greatly reduces resistance in the system, allowing more current to be transmitted, and less heat generation.
STEP 5: Install resistor across charge warning light at instrument cluster.
[discuss, photo?]
Lighting:
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....
ADJUSTABLE HEADLIGHT FOR FULL FAIRING BIKES:
One other improvement I have made to my R100RT model airheads is a method of easily and precisely adjusting the headlamp to account for changes in the suspension based on load, etc. My headlights are now bright enough, that if I don't do this there is a real issue with dazzling oncoming traffic...
I have a threaded rod, spring, & adjusting knob connected to the headlight shell and accessible just below the dashboard of the fairing. a few turns of the knob in the right direction and the headlight smoothly moves up or down, and STAYS there. Similar systems were used in later Vetter fairings, and are in current use on the Oilhead RT model motorcycles.
If interested, email me and I can provide more details about how this upgrade is accomplished. For a small fee, I may even be willing to provide you with a "kit" that will install easily.
Steering/Handling/Suspension:
First, make sure that all of your bearings are in good condition!
Clean, inspect, relube, and properly adjust your; front/rear wheel bearings, steering head bearings, and rear swingarm bearings.
If any of them are the least bit suspect when you clean/inspect them, go ahead and replace them. It is cheap insurance, and could save you wondering what went wrong when your steering still feels notchy...
After that, make sure that you have the preload set properly on both the front and rear suspension. My rule of thumb is that when you are loaded as you will be on the road, the suspension should be compressed about 1/3 of the way through its total range of travel. That gives some room to deal with holes, but more room for bumps which require more suspension travel. (Yes, your wheel will travel farther going over a 2x4 on the road than if the same size hole were made in the pavement. But that is a subject for another discussion...)
If your shocks are original equipment, chances are that they are tired or completely worn out. The "newest" Airhead is still 13 years old (1995), and some daily drivers are over 30 years old. Shocks wear. It is unavoidable, unless you don't ride. Getting a new set of shocks, even basic ones may make a surprising difference in the ride & handling of your Airhead. Getting higher grade shocks may make even more of a difference if you ride it in a more sporty manner. Consult with someone who knows shocks & our Airheads for more info.
Tom Cutter at Rubber Chicken Racing Garage knows Airheads, and races bikes. I would trust his judgment as to shock/spring selection. At last contact, he also distributed several brands. You can find his website at:
http://rubberchickenracinggarage.com/
One other thing that you can do to improve the handling of your BMW Airhead is to stiffen up the front forks. First on the list should be replacing the stock flat stamped steel top plate with a heavier top plate which will resist twisting better, and clamps the tops of the fork tubes. Second on the list should be getting a lower fork brace for holding the tops of the sliders in alignment more tightly. I personally prefer the "hoop" type slider braces as used by Reg Pridmore back in the day, and made famous by CC Products. I have heard rumors that SanJose BMW/CC Products is no longer manufacturing these excellent braces. If so, you will have to find a used set and make sure that the two sides are still parallel before mounting. Telefix braces may hold the distance constant between the slider tops, but they can do little to prevent twisting/torsion due to their design.
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:
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Ergonomics:
Check back for more info...
Special Tools:
I had bought one of those cheap cast aluminum exhaust nut wrenches from SanJose BMW because the price was right. Unfortunately, I do work on my bikes in a very cold uninsulated/unheated garage in the wintertime. I found out the hard way that these are cheap in more ways than cost. Mine suffered from brittle fracture in the middle of the handle when struck with a hard rubber mallet the very first time I tried to use it. I figured, Ok, I can still hit the shorter handle, and it is thicker there now where it tapers to meet the head of the wrench. Wrong! It broke off again even shorter... So, I was faced with exhaust nuts that needed to come off, and a wrench that was now in three pieces. I did what any true Airhead would do. I modified the remaining intact wrench head with a reinforcing steel plate with a socket welded to it so the wrench can now be used with a standard breaker bar! The steel was just a piece of scrap I had around, and an old oddball socket out of my tool tray which had seen better days... Total cost, 1-hr of my labor.
Brakes:
Easy Brake Bleeding:
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.
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Ones I have owned, present & past:
Will be adding to this as time allows....
Beemers: (in order of acquisition)
1990 R100RT - Bermuda Blue. Bought new, retired due to cager at 38,500 miles
1974 R75/6 - Avus Blue. Bought with 20,000, sold with 57,000miles.
1993 R100RT - Classic Black Metallic. Bought new, sold with 48,000 miles
1977 R75/7 - Black (the Rat). Bought with 98,000, sold with 108,500 miles
1996 R1100GS(A) - Black with Maroon seats. Bought New, sold with 36,500 miles
Still own the following:
1982 R100RT - Stratos Silver. Bought with 42,500 miles, currently 95,000+
2002 R1150R(A) Atlanta Blue - Bought new, currently 36,000+
1995 R100RT Classic - Final Edition of the Airheads. Bought with 47,000, currently 51,000+
1986 R65 - Blue. Bought with 10,600 miles, currently 14K+
Gee... I think it is time to apply for my 100,000 mile award... ;)
My 1974 R75/6
Sometimes you just need to carry a spare... My sidecar motorcycle carrier in action!
The fiancé's scooter being brought in for service.
BMW congratulates Harley-Davidson on 100years of business...
Please email me if you have any comments, suggestions or new ideas.
Thanks!
Dyna Beads
Champion Sidecars
