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$4 Carburetor Synchronizer

Since joining the Airheads shortly after purchasing my first-ever Beemer in October of 2001, I’ve found the AirList to be an invaluable source of information and direct feedback as I learn my way around my new 1984 R100RS. One of the first things I do when acquainting myself with a new mount is a basic tune-up. Lurking on the Airlist provided a bunch of helpful tips to supplement (and correct) the tune-up info in the Haynes and Clymer manuals.

One of the slickest tune-up tips I came across was Tom Rowe’s mention of a ridiculously cheap and easy-to-build differential manometer (vacuum gauge) for balancing carburetors on vacuum port equipped Boxers. I’d read about the Twin-Max (aprx. $80) and have used the $40 CarbStix on my 4-cylinder Hondas, but for less than $4, I was able to build a twin carb synchronizer that is 16 times more sensitive than my mercury vacuum gauges and can be assembled from common materials available at almost any hardware store. I built it and my R100RS loved it – it really smoothed out some bands of footpeg/bar/mirror vibration that the bike had, even after using the CarbStix.

I posted a ‘Thank You’ note for the idea on the AirList after I tried it and got even more valuable feedback from Jay Carpenter and a request from John “Beetle” Mailleue, ABC# 5657 to write a tech article for the AirMail. After spending some more time in the garage incorporating Jay Carpenter’s ideas, I figured I’d go ahead and write-up a description of how to build and use the $4 Carb Synchronizer, because it REALLY works. Super cheap, super accurate, super easy to build and super easy to use – CLASSIC Airhead technology!

Credit for the original idea has to go to Marty Ignazito of the powered-parachute crowd, he came up with the idea to balance the twin Bings on a two-stroke Rotax and his original write-up is at www.powerchutes.com/manometer.asp. If you try this idea and like it, send Marty a thank-you e-mail at mdipe@mcleodusa.net.

Here’s the Materials List for the $4 Carb Synchronizer Tool:

20 feet of clear plastic (vinyl) tubing – inside diameter big enough to slip on the vacuum nipple of your carb (3/16″ i.d. worked for my bike, but it’s tight, maybe 1/4″ i.d. might be better). 15 cents per foot in the plumbing section at my local ‘big box’ hardware store, Sutherlands.
A yard stick – Home Depot sells an aluminum yardstick for under $2, but you can make a perfectly satisfactory gauge with a 3-foot piece of 1″ wooden lathe for next-to-nothing. (For a ‘professional’-looking gauge, I actually used a yellow aluminum 4-foot rule, but that was wretched excess at $5.)
3M/Scotch/Whatever – clear mailing/packaging tape. You should have some of this left over from the Christmas mailing season; otherwise around a $1 a small roll (and you won’t need much).
2 short nylon zip-ties – You should have these in your garage. If not, buy them in bulk for cheap in the wiring section of Home Depot, Sutherlands, Ace Hardware, etc. – you’ll use them and wonder why you didn’t have them before.
A tiny amount of automatic transmission fluid – Actually, just about any fluid works, including used motor oil, colored water, 2-stroke oil, etc. I chose ATF because I already had a gallon of it and (most important) it is really thin and is RED (which looks WAY cool as the indicator fluid against my fancy yellow ruler) and ATF won’t hurt the engine if it accidentally gets sucked in the carb’s vacuum port.   (ed. note: 90W Tranny fluid works well and because it’s thicker – it’s less likely to get sucked into the carb.)

Building the Balancer

Fold your 20′ of vinyl tubing in half and mark the center point. Lay your yardstick down flat on a convenient work surface (kitchen table or floor). Place the center point of the tubing at the bottom end of your yardstick (there is generally a hole at the top end of the yardstick – put the center-bend of your vinyl tubing at the opposite end of the yardstick from that hole). Carefully run the tubing up each side of the yardstick, making sure that the tubing makes a smooth, non-kinked bend at the bottom.

Use the clear packing/mailing tape to fasten the tubing in place on either side ( left and right ) of the yardstick. Thread the zip-ties through the hole at the top of the yardstick and snug the left and right side tubing to the respective sides of the ‘stick with the zip-ties. You should now be able to hang your yardstick from the hole in the top ( I use a bungee suspended from a hook in the garage ceiling). The tubing runs around the perimeter of the yardstick and about seven feet of tubing hangs down from the left and right sides of the ‘stick. I fold a piece of tape around each end of the tubing like a little flag and mark the left side with an “L” and the right side with an “R” using a magic marker.

Now, put one side of the tubing in the container of automatic transmission fluid and, using the other side of the tubing like a drinking straw, suck ATF fluid about three feet up into the tubing. Maintaining suction for a second, pull the tubing out of the ATF container and then raise BOTH ends of the tubing above the top of the yard stick. Temporarily fasten both ends of the tubing high enough that the ATF drains down to the loop at the bottom of the yardstick. I recommend leaving it overnight so that all the bubbles, etc. work their way out.

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$10 Portable Wheel Balancer

However, last year I stumbled across a really great idea for a portable (you can put it in your under-seat tool tray) “Pocket Wheel Balancer” in an article written by Brian Curry on the IBMWR website. In brief, his balancer does away with the heavy, bulky balancing stand by mounting the balancing rollers on two little metal plates which are then hung from any convenient over-head support. The wheel and axle are placed on the suspended balancing rollers and balancing then proceeds as with a normal stand balancer.

Brian’s article is found at: www.ibmwr.org/otech/balancer.html and he deserves the credit for this very excellent idea.

My contribution to his original concept is to use readily-available materials — primarily ABEC3 skateboard bearings — and standard hand-tools for construction. A couple of hours worth of time in the work shop gets you a tiny, go-anywhere, use-anywhere, extremely sensitive (it will react to the weight of a 1/4-20 nut placed on the spoke of a snowflake wheel), static wheel balancer that only costs about $10.

Materials List

4 ABEC3 skateboard bearings
4 machine bolts, 8mm X 20mm (or 5/16″ X 3/4″), with nylock nuts and washers
2 machine screws, 4mm X 20mm (or 1/8″ X 3/4″) with a standard and nylock nut for each screw
8 inches of 2″ wide by 1/8″ thick aluminum bar stock
20 feet of nylon twine

Suggested Tools

hacksaw
electric drill with 4mm (or 1/8″), 8mm (or 5/16″) drill bits and 1-1/4″ hole saw
small steel square/rule
vernier/dial calipers (if you don’t have one, as an AirHead, you really ought to add one to your tool collection — you’ll find yourself using it all the time)
small file (or fine sandpaper, emery paper, etc.)
sharp scribe and center-punch — or just use a good-sized common nail

Building the Balancer

If you don’t have some laying around your garage, go to the local hardware store and get a short piece of the aluminum bar stock that is 2″ wide, about an 1/8″ thick and comes in standard lengths like 3′ or 4′ (you know the place in the store – usually has various sizes of aluminum and mild steel angle, straight, and channel stock in various sizes standing upright in slots at the end of an aisle). I got the three-foot length – it is enough to make 5 sets of balancers.

The center hole on skate board bearings is 8mm (or 5/16″). Get four 8mm (or 5/16″) bolts just long enough to go through the thickness of the plate, a bearing, an 8mm (or 5/16″) flat washer and a 8mm (or 5/16″) nylock nut (I used 8mmX20mm bolts, but 5/16″X3/4″ should work fine — 4 bolts, washers, and nuts total).

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Running Lights on a /6

I originally wrote this piece some seven years ago in 1995. Finding that the last of my modified bulbs burned out one filament the other day, I had to make some more up, which gave me an opportunity to revisit the article and to make it more useable.

Note that most if not all states require that any taillight or running light on the rear of a vehicle be RED as per D.O.T. guidelines unless it is used to illuminate the license plate.

The idea is to increase visibility of a motorcycle by the addition of two permanently illuminated rear running lights. Added to the central red light this gives three rear facing lights, allowing car drivers to triangulate on three light sources rather than one, enhancing their depth perception and improving the biker’s safety

I had fitted Full Scale Designs’ running light kit to the front and rear of my K100LT. A nice installation on a not so nice motorcycle, now sold and unlamented. The installation described here is not as elegant as FSD’s but is equally effective. It has the merit of being much cheaper. You can also buy a ready made kit from www.run-n-lites.com for $30 plus a $50 core charge (as of August 2002). I cannot find a listing for FSD.

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Headlight modulators

Headlight modulators are, or can be controversial, with differing viewpoints & arguments for & against. Some find modulators annoying. I believe that is, perhaps not always, folks seeing OTHER folks’ modulators, not their own. Some are concerned about oncoming drivers fixating on one’s modulating headlight & aiming for them, this seems to come from the idea that a motorcyclist tends to ride to wherever they fixate on. Studies have shown that adding lights at the rear (& in some instances the sides) of motorcycles makes them more visible and recognized earlier. For the rear, the lights should be red & as differentiated as possible between Run & Brake. Bright clothing, greenish-yellowish helmets, etc. …all have been shown to reduce accidents. I see no one arguing about ‘fixating’ on THEM.

Whether or not to install a headlight modulator on YOUR bike, is a personal choice; the USA government has not made them mandatory. My comments in this article apply to the USA, as headlight modulators may not be legal in some other Countries.

There ARE reasons that motorcycles are specified, since 1978 in California, & specified in many other States, to automatically, upon ignition turn-on, to power headlights ON, without having to manually turn the headlight(s) on. State law & Federal law are not necessarily the same thing, but, typically, Federal law supersedes. In this instance, always on headlights after a certain year model does apply. There is also an argument about certain cars, such as late models, having constant-on headlights …the argument usually is negative, as motorcyclists want only themselves to have such lights, to differentiate between them and cars. That’s a decent argument, but tends to favor modulators in use during the daytime.

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Adding Running Lamp To Turn Signals

This article deals specifically with converting the two Airhead rear turn signals into running lamps, while retaining the original turn signal function. Considerable information is applicable to a FRONT turn signal lamps conversion, if desired.

This article does not deal directly with conversions to the Classic K-bikes, such as the K1, K75, K100, K1100. MUCH of what is in this article on the physical modifications ARE applicable to K bikes, Oilheads, ETC. The K-bikes have a bulb-monitoring relay; which complicates matters, & information on modifying them is in item #2 in  http://bmwmotorcycletech.info/K-hints.htm.

Adding running lamp functions to the rear (and/or front) MAY add to safety. You get more lights, & you have two lights that are illuminated in case your one rear stock running lamp burns out; many bikes have only ONE rear running light & if it fails you might be INVISIBLE to cars coming up towards your rear; which is one of the arguments FOR this conversion. My primary argument against this conversion is that the turn function is, or can be, less noticeable to car drivers ….due to the running lamp function in the same lamp, same housing (could be separate lamps on fronts, some bikes). You must decide for yourself. Proper installation with proper color of lens & proper lamp bulb may negate such arguments.

The conversion may not be legal in some States,  ….if the lens is not re-colored to be RED (or the lamp colored red). Careful selection of bulb & possibly inclusion of reflective aluminum foil may improve brightness.

There are potential problems if not done well, the turn signals might then not be as distinctly different from the running lamp function. Properly done they certainly CAN be very distinctly different. Several ways to go about it, including a small unpainted or no red insert area, in the middle of the lens, or, a band across the center. One can find red bulbs plus use aluminum foil as a reflector, if desirable. The reflectors & lenses of the stock bike are OPTIMIZED for incandescent lamps, NOT LED types. I do NOT recommend LED lamps (of any type I have so far seen) for purposes of this article although wide angle LED lamp structures may now be available. RED LENSES have been available at times, almost a perfect direct replacement for your amber ones; you need only to provide a rubber gasket (easy and only if you wish to), and in a few instances about a minute of filing, depending on if plastic or metal case. The ones I have seen have an even better than stock amber lens light diffusion/reflection in the lens. Check such as Ebay. The ones I saw have number K22750 and K32724 on the plastic cover & were made by CoolBeam MTP; they are marked as SAE & DOT approved. These are hard to find in the USA. I have a set on my bike. If you find a source, PLEASE let me know so I can publish it here.

The conversions in this article are for incandescent lamps. You are free to experiment with plug-in LED lamps, but I have not done much experimentation so far.

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Accessing the Headlight Bucket

The fairing-equipped Airheads began with the 1977 R100RS. The headlight bucket is basically the same as in the unfaired models (except for later models not having fuses, etc., in the bucket). The bucket is not part of the fairing. On the RS and RT the bucket is located behind the front-most protective glass that is part of a ‘tunnel’ assembly with a large protective rubber molding with an outer glass, etc., whose design is such that it offers a relatively smooth front surface to oncoming wind, etc. The expensive 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, the headlight/bucket was quite far inwards from the front of the fairing, and thus the outer fairing tunnel 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, unless you have a good reason to do so!

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 just barely expose a phillips screw at each corner.    

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Recognition & Safety

Conspicuity …Recognition …Safety ….

This article deals primarily with improving recognition and speed of recognition…hopefully leading to action by drivers of ONCOMING vehicles (whether from your front, rear, or sides), but also covers how YOU see other vehicles.

Many safety agencies …and studies, …have proven that safety is enhanced for motorcyclists having modulated headlights …as the pulsing light attracts attention, particularly important to a motorcyclist, who wants, or should want, an oncoming driver to notice & recognize that a motorcycle is there. This has been shown to reduce left-turn accidents, & in general, reduce most biking accidents.

Studies have also proven that bright clothing and certain colors of helmets help reduce accidents considerably.

State and Federal Governments testing and reports is NOT extensive for motorcycles, nor is private/commercial testing/reports.  While many effects do cross-over between carts and trucks and motorcycles, the information is spotty about specifics for motorcyclists.  Further, there is a considerable amount of wrong ‘information’ in common use or understanding. Especially notable is the paucity of knowledgeable effects of movement and head positioning of drivers/riders of vehicles on recognition times; although there are other things, including lighting, colors, etc….and these are vast subjects.  Many of the technical details are in this article:  http://bmwmotorcycletech.info/hdlite.htm
The information in that article is extensive.   I HIGHLY suggest you stop here, and read that ENTIRE article, before proceeding!

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Tachometer, Speedometer, and Odometer Calibration

BMW odometers tend to be quite accurate, and all the speedometers EXCEPT the 85 mph ones (which are usually accurate), tend to read high by 6 to 12%.  This is ON PURPOSE by BMW. See the article hyperlinked just below, which is more detailed and has the information on why the inaccuracy, and MUCH more.  

Recalibrating a speedometer is a touchy job, of messing with such as hairsprings, and is best left to an expert.   

Speedometers/odometers have W ratios printed on the face, and they must correspond to the rear drive ratio, see the charts on the author’s website, which is more expanded than on this airheads.org website.   The following hyperlink to the author’s website has all the information you would want:

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Speedometer Repair

Thanks to all esp. Paul Glaves, Jeff Saline, and Randy Mallon

After some probing I found the upper RT silver gear that transfers drive from the total mileage to the trip odometer to be loose on the shaft and causing the trip odo to run intermittently. Using minimalist approach and a tooth pick I first carefully dipped the toothpick in alcohol and cleaned the shaft without disassembly. Steady hands and a watchmakers magnifying loupe helped. When that dried I put a drop of liquid crazy glue an a piece of plastic and using a toothpick I dipped it in glue and than transferred small amount to the shaft above the gear keeping it upright so capillary action will draw it downwards. I am now considering a good spot to drill a 1/4 inch hole and put a Gortex patch over it to try to get rid of fogging.

Jeff Saline cautions: One thing I don’t remembering anyone commenting on is allowing super glue the opportunity to out gas outside of the instrument housing. I haven’t ruined a lens yet but understand that if you use super glue and immediately reassemble the instrument housing the super glue will out gas and fog the instrument housing lens(es). I was repairing a high beam indicator blue lens the other day and have had the instrument out gassing for 6 days now. I recall hearing 24 hours is enough time

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Wiring Color Codes

This covers most of the basic wire colors used on Airheads.  As the electronics got more complex, more combinations came into play so it’s possible a few of the more obscure ones may see other uses.  Always double check factory wiring diagrams, and yes, even they can have a mistake or two.  PowerBoxer.de has a copy of the Haynes ones. And here’s a link for more about Airhead relays and terminal designations.

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