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14-B chitechelmnl.htm
CHITECH BMW ELECTRIC SCHOOL
MANUAL
NOTE: My comments are applicable to my copy which is dated 1993
on the front cover.
Synopsis: This is more like a factory school training manual. As
such it is really excellent. It contains a good basic electricity
primer and the BMW charging system in great depth. Also covers
almost 100% of the little things that are often left out of other
publications: emission valves, flashers, beepers, etc. The one
thing it does not cover in any depth is what happens ...or the
symptoms....when any particular part fails. That type of
information can be gleaned from postings of symptoms and the
cures, on the Airheads LIST, and also (blush) at places on MY
website that you are looking at.
Most of my comments or critiquing are really minor to moderate
nitpicking.
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 relatively
warm.
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 is used to preclude any
possibility of problems, and 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.
6. 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.
8. Page 56 and Page 57, Appendix E: Again, far too complicated
and 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 proper contact burnishing tool...or,
very fine grade SANDpaper, a 360 grit followed by 500 is OK.
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 14.5 for Panasonic battery), at roughly 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 the earlier Bosch mechanical
regulator, except underneath and inside, and 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 (let
alone aftermarket) accessory leads.
12. Page 64: The neutral switch is BELOW, underside, of the
transmission, on later models (5 speed).
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, and 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
here. While, yes, most think that the purpose of the capacitor is
just to reduce the sparking/arcing at the points, this is not so.
At the instant the points open, the capacitor, having previously
been shorted out by the points, is now exposed to the end of a
coil, containing a large magnetic field. The other end of the
coil is connected to the battery, and thus a complete circuit is
had. For very complex to explain reasons, the capacitor allows a
current flow from the coil primary winding, to ground, through
the capacitor. This 'reverse' current greatly intensifies the
transformation inside the coil windings that would otherwise be
poor without the capacitor. The capacitor does this at the very
instant of the points opening, lasting milliseconds ....as a
previously points-shorted capacitor ITSELF looks like a short
circuit to the coil, because the capacitor contains no
charge. The capacitor in a very complex manner, then charges up,
not quite as intensely, some energy is lost as the process
repeats back and forth for a bit, the spark plug fires, then the
process repeats somewhat, as the coil primary current oscillates
while diminishing, until it falls off to zero. See, told ya it
was complicated. The result, for the nerds out there, is a damped
waveform. BUT, it is this effect I am talking about here, that
causes the reduction in spark intensity if the capacitor should
fail by opening internally or a broken capacitor wire;...besides
causing rapid burning and pitting of the points. Should the
capacitor short circuit, the system has no spark output to the
spark plugs. Capacitors will usually fail as either an open
or a short, sometimes the short is not complete and the capacitor
would check as 'leaky'...that is, some resistance below infinity
on an ohmmeter. It is rare, but the capacitor MIGHT fail
intermittently...often with temperature change. Again, rarely, a
capacitor may fail by a REDUCTION of its capacitance...this
allows serious pitting of the points. The best test is to replace
it.
16. While working on my own 1983 R100RT, and comparing to the
schematic for same in this manual, I happened to notice an
error. There may be others. On this schematic, and
for just about every model and year actually, the Left and Right
turn signal circuits are shown as one dual-color wire coding for
the Left, and same for the Right. I found that the front and rear
colors are not the same. For example, the RIGHT wiring is
blue/black and also blue/green. The wires are joined at the same
crimped push-on spade connector.
This manual has been reprinted.
Go to the Club site for the manuals:
http://www.crbmw.com/content/view/22/46/
The
Electrics manual is now priced at $30, is simply THE best
electrics manual for airheads, and Oak was primarily responsible
for that manual. HIGHLY recommended.
There is my CRITIQUE of the electrics manual on this
site: chitechelmn.htm
Rev:
02/16/2007: update Chitech information
01/06/2008: same as above
01/07/2008: same, but url