About electrics on the bikes

Every time I try to develope a piece of the site I do not know what to tell about it, this takes a lot more time than coming up with a name for a page.
So I urge anybody who is better in one of the subjects, or English, to write something about the subject, so I can place it here for everybody to see.
The electric system starts with your batterie, because without power, the bike won't start
If you are working on your bike, check the wiring harnass, at least at the spots where it scratches over the frame and the connectors.
You might come across open, maybe even corroded wires (the insulation shrinks over the years)
Damaged insulation (that can be fixed with selfamalgamating tape (get it at your local boatshop ;)
burnt oxidised connectors, broken wires.
Clean everything out with contact cleaner, if a wire is very oxidized, cut it out and renew the piece (welding is preferable, then tape everything in)

Wiring basics
Most mechanics get the creeps when it comes to the electrical system on bikes, why I do not know.
But after some email with somebody who had a multimeter and a faulty boosy sensor, I think I know what you should know
(this is part of the information he send in to me regarding his measurements:....I set the tester to 1k ohms....Blue/orange wire no needle movement with ignition off. But, needle swings far to the right when the ignition is on. [Does this mean there is no fault in the wiring system a you thought?]..what can I say...i thought that owning one was knowing how it worked ;)
This part is for anybody who is not familiar with a multimeter.
First the multimeter, doesn't really matter what kind of, the cheapest one will do, if you haven't got one yet.
It has an Ohm scale, this means the batterie inside the multimeter is used to put some current on the component you are measuring.
If you use a multimeter in this setting you can measure a SINGLE COMPONENT, so this function is not meant to 'measure' your computer (toasting your computer however is possible, a new one is only 2000 euro, so go ahead and try it) or other complex things, you can however check disconnented wires and single parts (like a coil or a sensor)
The default is an 8 on it's side (endless resistance), when the two pins are making contact it should read 0 Ohm (other side of the scale, readjust if not a digital one ;)
NEVER use the Ohm scale to measure things that have some other power source connected.
If you are not sure what disconnected means at least pull out the batterie to prevent toasting the multimeter
The other interesting scale there is the DC scale, that's used when everything is connected, batterie loaded up.
This scale is meant to measure your bike (Except for the alternator, you need the AC scale for that in the range that coveres some 50 volt)
both scales probably have a X10,X100 choise too, this means if you measure 1.2 volt in X10 scale it's 12 volt, the same applies for Ohm, where KOhm is X1000.

Ok got that? let's try some testing here.
Take out a (working ;) lightbulb, place the multimeter (in the volt range) against the 2 contacts, - (black probe) of the multimeter against the metal housing of the fitting, + (red probe) against the other pole (make sure they make good contact, and not with themselves)
reading should be 0 volt, switch on the contact & lights (if you're holding the pins this might be trickey ;)
reading should be 12 volt, a bit more if your bike is running, a bit less if it's standing still, or you have bad connections.
Change the red and black probes and you'll see the digital one says -12 volt and the analog model want's to go trough the housing, indicating you shouldn't do this for long ;)
Now get a loose piece of wire, peferably half a meter or so, this will be your 'resistor'.
Place the multimeter in the Ohm Xmax scale and put a probe on either side, it will read as 0 Ohn because it is too little to measure in that scale
Measure it in lower scales and in the X1 scale you will find a value, probably around 0.4 Ohm or less.
Always start with the highest value if you are not sure what you are measuring, this makes the chance you damage some component that was not meant to have power on it to a minimum.
This value indicates that the wire is in a good condition, now cut the mantle of the wire somewhere, remove a piece and cut all small copper wires except for one.
Measure it again in the X1 scale, if only one small wire is connected, you'll see a much higher Ohm value (more resistance)
By bending wires and because they are getting old, there is always a chance that a wire breaks inside without you seeing it, this means you have to disconnect both sides of a wire and put a probe in either side,
Now measuring on the bike again, because if you measure a high resistance the wire must be broken, huh?
Put the contact back in the 'off' position, if you hadn't already.
Multimeter in the Ohm Xmax(10K? X10000?) scale, measure 2 different leads (if you were using the headlight for the other test, try the high beam and regular one)
Now you can see a value too, this doesn't mean there is a bad connection, no it means you are measuring the total leakage of all connected component.
Might be an interesting value, but you are not measuring anything in particular, no academic value ;)
told you everything there is to know...for starters.....

More about batteries

More about lightbulbs

More about switches

More about sensors

More, every time there's more to tell