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Accessing the headlight bucket on RS & RT,
via the Light Shaft with Molded Glass....
+ cleaning the headlamp assembly, re-aiming the headlight
on ALL models; accessing wiring and front fuses, etc.
© Copyright 2019, R. Fleischer
NOTE: The fairing-equipped Airheads began with the 1977 R100RS. The headlight bucket is basically the same as in the unfaired models (except later models not having fuses, etc., in the bucket). The bucket is not part of the fairing. On the RS and RT it is located behind the front-most protective glass that is part of a 'tunnel' assembly with a large rubber molding that is protective, and offers a relatively smooth front surface to oncoming wind, etc. The outer glass has some orange lines on it. There is no purpose to those lines (stories abound, all wrong) except to draw the eye away from the quite large front glass. While the orange lines were purposely installed for that stylish effect, one cause for that was that the headlight/bucket was quite far inwards from the front of the fairing, and thus the outer fairing tunnel hole glass needed to be of substantial size to prevent narrowing of the headlight beam. There is NO aiming or other purpose to the orange lines.
Don't do any disassembly of the fairing beyond what is noted below!!
1. Fold back, barely (just a small amount), one corner at a time, each corner of the rubberized material surrounding the $$$ glass in the fairing. That will expose a phillips screw at each corner.
2. Use a phillips screwdriver on the single screw in each of the 4 corners & loosen them fully, but leave them in place, fully loosened. DO NOT remove the glass, no need, and you are far less likely to accidentally break it.
3. Pull out the entire rubber headlight assembly we call the Headlight Tunnel. BMW calls it the Light Shaft with Molded Glass.
4. The two very large side nuts that hold the metal headlight bucket to the metal ears, are, even when tight (which they should be), acting against rubber washer-pads in such a way that the headlight bucket can be moved (rotated) up and down via some hand force, without loosening the large side nuts. The bucket is moveable for adjustment, without loosening those big nuts. If not moveable, you may be missing the rubber washer-pads, then you will have to loosen them a bit, and you should strongly consider installing the proper rubbers. Do NOT adjust the headlight aiming point at this time if you are going to open the bucket.
5. From the front of the motorcycle, grab the headlight bucket, and tilt it upwards, some, with your hands. Rotate enough to just allow a phillips screwdriver to access the screw at the bottom center of the front of the bucket at the outer chromed ring. That screw holds the headlight and reflector/chrome/assembly to the bucket. Loosen a few turns ONLY ...do NOT remove the screw.
6. Lift the chrome ring with the headlamp and reflector and headlamp lens outwards and upwards from the bottom, and remove the electrical plug going to headlight lamp, while the lamp is still mounted to the reflector. The lamp plug is usually fairly tight and if you intend to remove the plug, move it back and forth only a small amount at a time as you pull on the plug (Do NOT pull on the wires).
You now have everything in front of you. What you see depends on your year and model. Pay attention to how the chrome ring fit into the top of the bucket, and how the phillips screw works at the bottom...and, notice those weird wire clips that contain the headlight glass to the chrome ring. NOTE that the main lamp (there MAY be a side small lamp if someone installed it) is a 55/60 watt H4 Halogen, similar to a type 9003 (the Euro lamp versions are better, see my lamps article, https://bmwmotorcycletech.info/lamps.htm)
It is not a good thing to increase the wattage of that lamp without first adding relays. Eastern Beaver has a great plug and play relay kit, with a direct power wire, that will increase lamp brightness some, and you can use a larger wattage lamp if you want to. The reason not to use a larger lamp wattage withOUT the relays, is that it will overload the expensive light switch on the handlebars.
Except on last of the Airheads or some earlier R45/R65 models, you probably you will see the flasher relay on the left, headlamp relay on right ...as you face the open bucket. It is a good idea to be sure all wires are tight, nothing loose, the two fuses are making good contact. The fuses are elsewhere's on the last of the Airhead motorcycles, typically at the rear, below the tail of the fuel tank. If the fuses are not making good contact, then remove, clean/burnish fuses and prongs with a common eraser. DO NOT break the fuseholder prongs. You may carefully bend them a bit if needed, they must grip fuses moderately tightly. I usually JUST rotate the fuses with my fingertips, so as to have the pointy tips of the fuses rub a bit in the holder, which helps clean the contact area. The German style ceramic fuses, with the unprotected fuse element, are FAR MORE reliable than American pointy cap fuses due to how the fuses are constructed internally. The fuses are rated at 8 amperes each, and up to 16 amperes are generally safe to use if you have accessories on those fused circuits. Don't increase the fuse size unnecessarily. The fuses are NOT in the headlight circuit except in certain models prior to 1978....but this is difficult to explain, and is explained in depth in another article.
Looking at the headlight assembly, you will see some 'strange' metal clip wires I mentioned earlier, used against the folded metal rim and the glass reflector assembly. Do NOT try to separate the front from the rear of the reflector assembly, as you are likely to break the reflector assembly glass, and you do not need to separate them for cleaning. Do pay attention to the metal wires that hold the glass reflector assembly to the metal rim ...and note, specifically, that they must be installed so as to not interfere with the top bucket short upwards depression area where the rim hooks onto; and, the bottom area where the friction clip is, of which you loosened the screw earlier.
Now you can remove the headlight lamp bulb, there is a wire clip to move, then the lamp comes out. The lamp is located by tabs on the lamp metal base. The lamp is a halogen type, and the quartz glass runs VERY hot in operation. YOU MUST clean that quartz glass using home alcohol and a clean rag, before replacing the lamp, and do NOT allow fingerprints on the glass envelope! The insides of the reflector are often fogged slightly or more that slightly, and cleaning is a good idea, if you do it carefully. Clean the inside of the reflector with home type isopropyl rubbing alcohol and a very soft swab and also, as noted, clean the lamp glass before re-assembly. Do not scratch anything, nor leave fingerprints or anything at all on the quartz glass nor reflector nor the halogen lamp itself when you reinstall it, and, of course, the reflector and inside the glass must be completely dry. Note that any fingerprint oil, in the slightest, on the quartz glass lamp, will reduce lamp life. Curved forceps help with the cotton swab, but be careful! The reflector surface is easily damaged from metal tools and even from coarse cloth. Because of the danger of damage, you may want to make up a mixture of perhaps 1/4th cup home rubbing alcohol and 1/4th cup of water, and 6 small drops of liquid dish detergent, or liquid hand soap, and swish it around instead of using a swab, etc. Wash out thoroughly with plenty of water and allow to totally dry. If you have high mineral content water (often called Hard Water), use distilled or purified water. After shaking out all the flushing water you can, you can consider using a hair dryer on the lowest heat setting, but do not allow overheating in the slightest! Some owners will try to separate the glass and reflector that I cautioned you not to do; it is tricky to separate and get back together, and trying to force them apart often results in $$ glass damage.
Clean the inside of the protective glass in the forward area of the tunnel, any common cleaner, ammoniated or not, and even detergent in water, will do for that glass. When you are sure you have no cleaning streaks left, reassemble.
NOTE!!! When replacing the headlight/ring/assembly, it "hooks" first at the top, there is a upside down depression for that. After hooking at the top, you will have to hold a bit of pressure on the assembly at the bottom, while you tighten the phillips screw at the bottom. Do not overtighten that screw. Be sure that the ring/glass/lamp assembly is fully home to the bucket, by holding it so with your hand. If it does not want to be fully home, loosen the screw again, perhaps one more turn than before, and try again, while holding the assembly to the bucket more strongly. I already warned you about the weird clips placement to not have them interfere with the top fitment and the bottom screw area fitment.
Adjusting the headlight:
Most people simply grab the headlight bucket from in front before replacing the Tunnel rubber assembly, and move the headlight to an approximate position. Later, from the rider's seat position, they push it to the "desired" light output position on low beam. I'm OK with that. For the purists, or more nerdy (like me), etc. ...there is an official method ...which places the light in a legal illumination position. If you don't do it properly via guessing or measuring, the lighting may be poor.
Here is the official way to adjust the headlight (ALL models):
On your flat floored garage, make a mark on the floor, 5 meters (16 feet 5 inches) from a vertical wall.
Sit on your bike, with a normal load, that means balancing and having your feet on the pegs as best you can, so the bike's suspension is loaded by its normal load. You only need to balance for a very brief moment. Use a buddy's help, if you need it.
With your buddy's help, measure the distance from the center of the headlight outer glass to the garage floor. Put a mark at this same vertical distance on the wall, and add another mark 5 cm (2 inches) below it.
Move your bike until the front axle is directly above the 5 meters (16 feet 5 inches) floor mark. Aim the headlight for the two wall marks, balancing, with your normal weight and load as previously. The bucket should be adjusted for the cutoff to dark area on top to lighted area, to be between the two marks.
You can do it all yourself with a bit of masking tape or a pencil mark, balance & look, put bike on sidestand while you make marks or whatever....., measure, reset headlight, repeat, etc. etc.
Below is a scan of a factory service book sketch that may help you visualize the above information...note, however, that the sketch shows the riders feet on the surface, instead of the pegs.
© Copyright 2019, R. Fleischer
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Last check/edit: Monday, July 22, 2019