snowbum – Page 2 – Airheads Beemer Club

Basic Electricity 101+

The below article was written to furnish THREE types of information:

(1) CONSIDERABLE amount of BASIC & SLIGHTLY ADVANCED INFORMATION on electricity & Airhead problems. The approach used here is probably different than in most manuals & troubleshooting guides. Although some hints are given in this article on some common faults, this article should be used in conjunction with my other articles, particularly: http://bmwmotorcycletech.info/electricalhints.htm

(2) Common problem areas, explanations of some of the circuitry. A discussion of such as batteries; starter motors, voltage regulators, etc. Other articles will get far deeper into these things.

(3) An addendum that may discuss particular points that has come up, or some topic of interest. Some is at the very end of this article.

Available to you are certain helpful booklets from such as Motorrad Elektrik, Chitech, Haynes and/or Clymers manuals (and, perhaps, a schematic in the rear of your owners booklet or on the Snowbum website). In my opinion the Chitech electrics manual and the owners book or factory schematic, or schematics on the Snowbum website (and some elsewhere’s, and I have links to these on the Snowbum website), are THE BEST sources for electrical information for the Airheads.

I recommend you at least purchase at the Chitech Electrics Manual. The Chitech (Chicago Region BMW Owners Assoc.) BMW Electric School Manual is THE BEST manual for BMW electrics, from basics to full-blown technical details, components, diagrams, etc., & includes the singles & all Airheads; even some on the /2 era. It is VERY complete. Only a few errors, for which i wrote an article/Critique: http://bmwmotorcycletech.info/chitechelmnl.htm

See http://bmwmotorcycletech.info/url.htm for more information on Chitech, and how to order their publication. Some of the total-bike schematics are not reproduced well, that is the only substantial problem with that manual. Get the manual anyway.

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Albert Mirrors

.pdf diagram of assembly and parts for the SPORT mirror:
AlbertBarendPartsDiagramSport.pdf

.pdf diagram of assembly and parts for the TOURING mirror:
AlbertBarendPartsDiagramTouring.pdf

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Cleaning Exhaust Systems

Cleaning Exhaust systems:
Pipes, headers, mufflers, etc., can all be cleaned with 0000 grade of steel wool. Use of 000 grade should be reserved for the worst cases. Exhaust pipes polishes to reduce bluing are available, most do little, and the bluing tends to come back soon. A particular problem is that exhaust systems tend to get oily grunge & other fun stuff such as burned boot heel material on them that gets thoroughly baked onto the surface. Late model Airheads have pre-muffler/collectorson which can can be ‘wire brushed’ with a steel or brass wire wheel/brush, but they are more abrasive to the surface. Brass bristled brushes are safer. Wire brushes may be your last resort if items are truly a big mess, this is particularly so if your items are chrome plated steel & are “rusting”. Strong chemical means, which will not eat the metal like steel brushes will, work well for heavily baked-on oil/grease/etc. I HIGHLY recommend the entire process be done OUTDOORS.

Clean off any oil/grease you can, with a petroleum solvent. Kerosene; paint thinner; Stoddard solvent; MEK; Acetone; whatever you have. Wash with very hot water & strong dish washing detergent mixture. If the items are still mounted in your bike, you want to mask off, by whatever good means, the bike from the next step. You do NOT want any aluminum castings getting strong ‘oven cleaner’ on your castings, etc.

Obtain a spray can of OVEN CLEANER. Get ONLY the type containing sodium hydroxide (common household lye). Rarely, these days, you might find potassium hydroxide, it is also OK. NO OTHER TYPE of chemicals but these two provides seriously strong chemical cleaning against burned-on grease/oil. Sodium bicarbonate is NOT going to work hardly at all.

If you can, warm the parts to be cleaned. The hotter the parts, the faster the stuff works…but, NEVER higher than water boiling temperature. YOU ABSOLUTELY MUST WEAR SAFETY GOGGLES!! If any spray gets on you, WASH IT OFF, right now, NO waiting. KEEP IT OUT OF YOUR EYES. Try hard NOT to breathe the spray. Spray the surface generously. DO NOT BREATHE-IN, WHILE SPRAYING. How fast the chemical works depends on temperature and that it remains wet. It is OK to use a foggy spray of water to keep the chemical wet, if it is showing signs of drying. In particularly egregious cases you want a thick layer plus you want it covered so it will stay wet, perhaps overnight. The chemical must be wet. It is better to do this job with the parts off the bike, but that may be inconvenient. After a while, perhaps 15 minutes or longer, wash off very thoroughly with water. Use a stiff floor scrubbing type of brush or modify a stiff paint brush by shortening the bristles so it is even stiffer. If the wet surface feels soapy/slippery, it is not washed off enough.

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19 inch FRONT Snowflake Wheel Recall

UPDATE: The silver replacement wheels are no longer available (36-31-1-238-959). Gold wheels are available and the recall will be honored. 36-31-1-238-960.

19 inch FRONT CAST ALUMINUM SNOWFLAKE wheels were recalled. NOT 18 inch front wheels. NOT 18 inch rear wheels. Recall is ONLY for certain AIRHEADS 19 inch front cast aluminum snowflake wheels.

I still hear occasionally about an old recalled wheel that is still in service. There was a BMW factory recall on SOME FRONT 19″ cast snowflake wheels, & only those! Supposedly a U.S. Federal Recall Campaign never goes out of date. The RECALL is world-wide, & there are specific recall campaigns in the various countries. BMW will provide the recall service, as described in this article, for the BIKE, the bike identification is needed……..AFAIK! I have yet to hear of/from anyone who brought in a wheel to be exchanged & the wheel was not tied to a specific bike identification. You could be the first to tell me the details!

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Experience with DOT 5 (Silicone) Brake Fluid

Do any of you have personal experience with DOT 5 brake fluid in Beemers? If so, I’d appreciate hearing from you, as to whether it was good or bad. In the meantime, I’ll share mine with you.

My bike is a 1974 R90/6, purchased in December 1976 with 5k on the odometer. It has a single-caliper front disc brake. Removal of the fuel tank to top-up the brake fluid four months later revealed a jet-black liquid in the brake system, which I flushed out with clean DOT 3. Occasional checks thereafter revealed that the fluid in the reservoir remained clean and clear, and there were no leaks in the system. By 1981 (31k), the fluid in the reservoir was starting to look like Sierra Nevada pale ale, so I flushed the system again with DOT 3.

In 1982, having had good luck with silicone (DOT 5) brake fluid in a 1971 MGB and a 1966 Buick for about three years, I decided to try it in my bike. Advice to the contrary notwithstanding, I disassembled the master cylinder and front caliper, found the pistons and cavities clean and bright – no rust or corrosion – wiped out all the old fluid with a clean rag, washed loose parts with soap and water, reassembled using the original seals, and filled the system with DOT 5. There had been a very slight seep between the master cylinder and the reservoir, but decided that it wasn’t bad enough to go to the trouble of removing the reservoir.

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Broken front & rear brake light switches

This article is not concerned with the hydraulic pressure activated brake switches. Those switches, originally 34-31-1-233-959, were replaced with 61-31-1-244-334. You can probably substitute the switch used on old VW Beetles. Napa carries that switch as number SL143. There are other such switches: 3 terminal version is NAPA SL159, VW 113945515G; 2 terminal version is NAPA SL147, VW 0344004003.

This article IS concerned with the mechanically activated brake switches. All R series bikes FROM 1985 model year through 1988, & SOME 1989 Airheads were affected. ALL models of Airheads for those years!

BMW Service Information Bulletins were issued regarding the front & rear brake light switches, brake lever, etc. The bulletins applied to both Classic K bikes & to Airheads, but not exactly the same way. There were bulletins issued in 1987, updated in 1988 & a formal recall in 1989. Later bulletins were longer, with more details.

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Brakes

This long & extensive article covers both disc & drum brakes. There is a lot of information for 2-wheelers, some for sidecars & tugs. There is a complete discussion about brake fluids & bleeding. Much is applicable to any hydraulic brake system. Included is squealing information for motorcycles, especially Airheads, other bikes, Bulletins for K-75, Etc.

Warning: working on brakes is serious business. Read this entire article, perhaps more than once, before you begin work on your brakes. If you do not feel competent, take your bike to a qualified shop.

Broken cable or lever operated brake switch? (NOT the hydraulic switch). Brake pedal bolt not contacting the switch properly? (and it’s not a bent tube at the frame): http://bmwmotorcycletech.info/brakeswitches.htm

Regarding the hydraulic pressure activated brake switches: Those switches, originally 34-31-1-233-959, were replaced with 61-31-1-244-334. If you haven’t access to the BMW part, you can probably substitute the switch used on old VW Beetles. Napa carries that switch as number SL143.

FRONT DRUM BRAKES:

An article written by Duane Ausherman discusses assembly & adjustment of the 1955-1976 front drum brakes, with some applicability to the rear drum brake, & drum brakes after 1976: http://w6rec.com/

In my article that follows, below, I have numerous sections where I get into things Duane did not, regarding the drum brakes.

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Rear Drive Ratios

Variables for the chart are your actual on-the-road tire diameters (modest effect); tire pressures/temperature (tiny effect). The variation in UNLOADED diameter of a 4.00-18 rear tire versus a 120-90×18 rear tire is about 15 mm in the WORST case I know of. However, the actual rolling circumference varies little (probably about 2%, but could be larger). Hence the values shown below are THEORETICALLY fairly accurate, and some are taken from a BMW chart dated 1978, others are calculated, and some are actual test data. Values are theoretical; and do NOT account for tire slippage and tire variations, nor for speedometer and tachometer variations. Because of these factors, rpm is LIKELY higher for a true speed as charted.

See notes at end of this article!! The speedometer ratio is printed on the dial of most speedometers. The author’s website discusses things in much more depth, and includes expanded ratios for earlier models, etc…..link at the end of this article.

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Driveshaft Bolts, the split lock-washers…..and, push-starting cautions

The four TRANSMISSION OUTPUT FLANGE BOLTS CHANGES;…split lock washers, updates, …and….pushstarting! © Copyright 2021, R. Fleischer https://bmwmotorcycletech.info/drvshftboltstoolstorque.htm 47 Background and History on these 10 mm 12 point bolts and lockwashers used at the transmission output flange: The earliest bolts for the /2 & the Airheads (transmission output flange-to-universal joints) had steel split-type lock-washers, & were […]

Throttle & Clutch Cables

In my shop I saw many control cable failures from these things.

1. Throttle cables on the Airheads: Left cable failing at the carburetor, due to the throttle cable being bent as owners checked the oil dipstick. Do not bend the throttle cable at the left carburetor when checking your oil. There is no need for the oil dipstick to be overly-tightened. Bending the left throttle cable is a prime cause for that left cable to have increased friction, possibly spread some coils on the wrapped sheath (& making that carburetor difficult to synchronize, if bad enough), & eventually you might break an inner strand …usually where you can see it between the throttle lever on the carburetor, & the sheath. A single strand found broken (You do inspect these cables regularly, don’t you?), will usually cause other strands to eventually break from the same reason why the first strand broke ….this will …or can …result in total cable failure in as little as few hundred miles or so.

2. The bushing at the clutch lever at the handlebars is a replaceable plastic part and as it wears the result is the lever can move up and down & also allow angular motion. If worn enough, the stranded core of the cable will start rubbing, or even catching, on the sharp edged guiding slot in the lever. Eventually a strand breaks, failure comes soon as more strands break. The bushings are easy to replace and not expensive. If your new bushing does not finger press into place, heat the lever first. The Nylon-like bushing is 32-72-1-232-662 and has been used from 1976 onwards. That bushing may need light reaming for a good fit to the pin. If you do not have a 8 mm tapered ream, you can use very carefully selected drill bits, to progressively remove a quite small amount of material, a few thousandths at a time …until the pin fits properly …an easy, but not loose, push-sliding fit. The lever has a recess, and in that recess must be a waverly washer, 32-72-1-230-871. I recommend the sharp edge of the slot in the clutch lever be filed smooth. Be sure the crimped end of the cable that fits into the clutch lever at the handlebars is not fouling the lever.

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