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Critique of the Chitech BMW Electric School Manual
© Copyright 2020, R. Fleischer
This is what the publishers (Chicago Region BMW Owners Association) say, and I mostly, but not entirely, agree:
The Electric Manual is actually a textbook-style educational manual rather than a service/repair manual. CHITECH believes the main reason so many riders have a hard time solving electrical problems is that they don't understand how the circuits work. This manual attempts to solve that problem by providing simple explanations in layman's terms.
Fourteen chapters, each covering the operations of a different BMW circuit, are understandable with only a basic knowledge of electricity. Contains 21 fold-out wiring diagrams covering BMW models from 1955 to 1990, from the R26 to the R100. The main chapters concentrate on the theory of operation and the appendices contain information more specific to servicing. Three of these appendices are devoted to troubleshooting procedures for what most owners find to be the most difficult circuit of all, the charging system.
The manual has been reprinted and is again available: https://www.crbmw.com/chitech-in-the-beginning/
The Electrics manual is $30. This manual is the best electrics manual for Airheads. Oak was primarily responsible for the manual. This manual is highly recommended by me, Snowbum.
My comments below are applicable to my copy which is dated 1993 on the front cover; and maybe to yours, if the manual is the same inside. Do let me know if your manual is not the same as mine ....when comparing my pages and notes, below.
This is more like a factory school training manual, and as such it is excellent. It contains a fairly extensive basic electricity primer, which is not mentioned in the statement by CHITECH. If you combine it with reading my article https://bmwmotorcycletech.info/boxerelectrics.htm; and, https://bmwmotorcycletech.info/multimeters.htm; and, some of my other electrical articles, you will be 'over the hump' on understanding electricity, and how to begin analysis of electrical problems.
The Chitech Electric School Manual covers your Airhead electrical system in depth. A fair amount of some of the /2 era is covered too. It also covers most of the things that are often left out of other publications: emission valves, flashers, beepers, etc. There are quite a number of pages in the Appendix area, covering most of the things you might also want to know ...or need. It does not cover in depth what happens ...or the symptoms ...when any particular part fails, nor all parts failures, but it does cover them OK. That type of information can be gleaned from postings of symptoms and the cures, on the Airheads LIST, and on my website https://bmwmotorcycletech.info. Certain accessories are also not covered, such as the wiring for the fold-out Authorities lamps; and, Authorities models where they differ from the civilian models. This is not of much importance, and all is covered by my website anyway.
Most of my comments or critiquing are really minor to moderate nitpicking. If you have a copy of this excellent manual, you may want to write these critique changes in your manual in pencil.
1. Page 6: The right side paragraph with the analogy with the 6 cylinder radial engine: This is very confusing and should be totally crossed out.
2. Page 8, section (1): The regulator senses the output of the 3 small diodes on the diode board.
3. Page 13, paragraph 3 on the left side: electrons do not flow quite as easily in acid. ...also, the 4th paragraph: There is also a small leakage current, which self-discharges the battery, which on many conventional 'wet-sloshy cell batteries' (called flooded batteries officially) can be as much as 1/3 of the total capacity per month if the temperature is quite hot.
4. Page 22, paragraph #1: "extremely" should be "relatively". ...also, for item (4), the inductor function is not explained. It is primarily there to reduce the contacts electrical noise...and somewhat the pitting. In this usage, the inductor has nearly the same effect as a capacitor wired across the contacts [THAT is not done as if the capacitor should short, serious problems could occur], and the inductor would be highly unlikely to short, but might open, which would be immediately noticeable in the charging.
5. Page 33, right side, next to last paragraph: Says that a higher coil current is needed for dual plugging conversion, and that the points are not capable of this. A higher coil current is not needed, but in practice it may be used to preclude any possibility of problems, & keep the coil size reasonable. A minor technically nerdy point only. A higher current IS bad for the points, but higher primary resistance coils could be used. I don't recommend that, as the coil output MIGHT be too low for solid ignition performance....I don't know of any large magnetic structure dual output coils being available at present, so this whole comment is strictly from an engineer's viewpoint. It is entirely possible to use a proper dual coil with points, or two dual coils with points, and by the time you read this, likely are available.
6A. Page 40: Second paragraph, left side. The flasher is load dependent, as far as the indicator is concerned.
6B. Page 43: The oil pressure lamp switch in my own information files, which might be wrong, show a much lower pressure for lamp operation, and nothing is said about the switch re-closing at an excessive pressure.
7. Page 53 through page 55, the section called "Dynamic Test Procedure"...up to item 14: This entire section is basically OK, but vastly too complicated for the average person. A far better method, giving better and easier results, is the fixed output voltage non-adjustable transformer and lamp method. This was outlined by OAK in some detail, in the June 1999 issue of Airmail. I treat it on my website too, including a sketch.
8. Page 56 and Page 57, Appendix E: Again, far too complicated & involved for the average owner. I suggest leaving it intact for reference, but using the following method to replace the entire Appendix E:
a. Burnish contacts with contact burnishing tool or, very fine grade SANDpaper (360), follow by 500. Burnishing does not mean sanding the contact hardly at all....it is not much more than a cleaning-up. Notice the grit grades I recommend.
b. Clean the contacts with a single drop of a good fast evaporating solvent, placed on a non-glazed tiny piece of absorbable non-linting paper.
c. Adjust the "bending bar" for 14.1 to 14.3 at high rpm (higher, perhaps 14.4 for a Panasonic or Odyssey battery), at approximately 70 degrees at the regulator (before the bike engine block is fully heated) ...as measured at the previously and recently fully charged battery. Do not short-circuit any part of the regulator. Use needle nosed pliers.
9. Page 61: El. Amplifier on 1981-84 models: Some models have this centered, on a pedestal, under the tank.
10. Page 62: El. Voltage Regulator: Some 1981-1983 models are in a metal box, that looks similar to earlier Bosch mechanical regulators (except underneath & inside), & is shorter.
11. Page 63: An 8 ampere fuse may be found in the connector leading to the accessory socket, as well as on some factory (and aftermarket) accessory leads.
12. Page 64: The neutral switch is below, underside, on the 5 speed transmission.
13. Page 66, left side, paragraph #2: el. behavior is same under same conditions everywhere. [This is a real nitpick].
14. Page 68, left side, paragraph #2: early English machines were + grounded.
15. Page 68, last paragraph on left, & first paragraph on the right: There is a much more complex operation of the capacitor also involved, that I am NOT surprised was not noted. Most think that the only purpose of the capacitor is to reduce the sparking/arcing at the points; but, this is not so. Yes, the capacitor (condenser) does reduce sparking. But.... at the instant the points open, the capacitor, having previously been shorted by the points, is now exposed to one end of the primary winding of the ignition coil. The coil & iron core are likely fully saturated with a large magnetic field. The other end of the primary winding coil is connected to the battery & thus a complete circuit is had. The capacitor allows a current flow from the coil primary winding as the magnetic field collapses, to ground, through the capacitor at the instant it appears (for a very short time period). This 'reverse' current greatly intensifies the transformation inside and between the primary and secondary coil windings that would otherwise be poor without the capacitor. The capacitor does this at the very instant of the points opening, the effect lasts only milliseconds, as the capacitor 'charges up'. The capacitor, in a complex manner as the points open, will charge, with some energy in the coil being lost as the process repeats back & forth for a very short period of time as the spark plug fires. The process repeats somewhat differently, as the coil primary current oscillates while diminishing, until it falls off to zero. What I have said here is not exactly what happens, but I am trying to simplify the explanation. The result is what is called a "damped waveform". Damped means just what you might think, if thinking of mechanical shock absorbers in your bike's suspension. For our purposes here, just assume the electric output looks like a sine wave train, with each succeeding sine wave being considerably smaller in amplitude. It is an AC (alternating current) waveform, and the coil can act, and does act, like a voltage step-up transformer (a LARGE step-up!!). An electrical/electronics engineer would think of the circuit as a Low-Q resonant circuit....which I am not hardly going to get into, here!
If the condenser should fail by opening internally (fully or partially) or by a broken wire; there will be rapid burning & pitting of the points. There will be a large decrease in high voltage output from the coil. Should the capacitor short circuit, the system will have no spark output to the spark plugs. Capacitors will usually fail as either an open or a short or sometimes the short is not complete & the capacitor would test as 'leaky'...that is, some resistance below near infinity on an ohmmeter. Capacitors can fail intermittently, often with temperature change. Rarely, a capacitor may fail by a reduction of its capacitance (partial internal opening)...this allows higher and faster than normal pitting of the points. The best test is to replace it.
16. While working on a 1983 R100RT, & comparing to the Chitech manual schematic, I noticed an error. There may be others. On this schematic, & for just about every model & year, the left & right turn signal circuits are shown as one dual-color wire coding for the left; same for the right. The front & rear colors are not the same. For example, the right wiring is blue/black & also blue/green. The wires are joined at the same crimped push-on spade connector.
17. One particular thing about the Chitech manual annoys me...many of the schematic diagrams for specific bike models are not sharply printed, they are blurred some, or think about it as out of focus. I do have a number of the schematics on this Snowbum website that are much sharper & easier to use, & most are in quite large pdf format, making them much more usable. I also have links to other diagrams.
Do not let my criticisms keep you from purchasing the manual.
My own copy is highly marked-up.
Here are a few more things to pencil into your manual:
In the Table of Contents, Chapter 10 has information on the clutch & neutral switch sketches; Chapter 14, under Fuse Protection, see BOTH pages 43 and 63.
Appendix I contains the 1975-1976 error sketch.
Page 30, figure 10-4. Note that if the brake failure lamp shorts, & the brake fluid level switch closes due to low brake fluid, or a switch failure, the starter relay will close when the ignition switch is turned on & kill switch is on.
Page 30, figure 10-5. Note that the neutral switch is closed in neutral, & the clutch operated switch is closed when the lever is pulled-in.
Page 39, Figure 13-2. The fuse was installed from mid-1972.
Page 40, Figure 13-3, the full circuitry inside the flasher unit is not shown.
Page 41. The R65 had TWO SEPARATE indicator lamps; similar to the other models, like R80ST, ETC., that had the new-style instrument pod.
Page 59. You can put a test circuit for the /5 repeat-start VR relay on this page, or the backside. Connect both terminals 15 & 30 to a source of +12 volts. Connect terminal 87 to a 12 volt lamp ...I use an old headlight lamp. Connect the other side of the lamp to terminal 31b, & the junction to battery negative. If you connect terminal D+ to the +12 volts, the relay is off. If you instead connect terminal D+ to -12 volts, the lamp is on.
Rev: © Copyright 2020, R. Fleischer
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Tuesday, December 15, 2020
02/16/2007: Update Chitech information.
01/06/2008: Same as above/
01/07/2008: Same, but url.
11/20/2009: Slight updates and clarifications. Also add #17.
09/23/2012: Add language button, QR code, update Google code.
07/31/2013: Split 6 into 6A and 6B, 6A being new information.
12/27/2015: Update crbmw hyperlink.
02/04/2016: Recheck link & price. Add table at top. Narrow article. Add notes a>h in item 17. Revise other items slightly.
05/22/2016: Update meta codes, scripts, layout.
08/19/2017: Clean up html, colors, format, layout.
© Copyright 2020, R. Fleischer
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Tuesday, December 15, 2020
Last check/edit: Tuesday, December 15, 2020