Modern Vespa

I am one of those people trying to wire all my mods on my own. As this forum is FULL of information to help me finish what I want to do, I was wondering if any of you know of some literature I should read to get a better understanding on wiring the bike?!!?

I know that I am supposed to have the fuse for my horn as close to the battery as possible, but why!? I know i need a relay for auxiliary lamps, but why!? I know I need to fuse everything, but what AMP fuse do I use?! and why?!

These are the things I would like to learn.

Of course, taking a course at a community college or what-have-you would be more effective, but that requires a bit more of an investment time-wise that I can dedicate to wiring a couple things.

THANKS TO ALL!!

The one thing to remember about fuses is that they are there to protect the wires, not the accessories. In case of a short to ground, you want the fuse to blow to prevent the wire from getting hot and melting insulation, or worse, starting a fire. The closer any fuse is to the battery, the better. Any wire between the battery and the fuse is unprotected and a potential fire starter. Have a look at this thread: GTS 250 ie electrical problem - smoke but no flames. So, when you're adding an accessory, find out how much current it draws, choose a wire gauge size that will pass at least that much current, and fuse the wire at or near it's "ampacity".
You would use a relay to power any high-current accessory to protect the on/off switch. Relay coils draw very little current and can be controlled with a relatively light switch. Relay contacts, though, can switch much heavier current. So with a relay, you can control a heavy-current accessory with a small switch.
Here's a good book: http://www.haynes.com/products/sfID1/8/sfID2/36/productID/56
Hope this helps...

Thank you sire!

Anyone else?!

You might also check out this terrific site:
http://www.allaboutcircuits.com/
The name pretty much says it.

Oh stop it...
Take it to your mechanic and take a 12pak of Beer

Quite. If you don't 'get it' by the age of about 9 then frankly don't bother. This may sound harsh but it is somewhat true.

Put it this way, if you are just old enough to ride, but don't understand some electrical basics, then it may be too late to ask a teacher to give those first vital clues.

It may not be though, some come good late in life. These are rare...

A very basic beginners book on understanding 12-volt circuits that I've found helpful is "The 12-Volt Bible for Boats" by Miner K. Brotherton and Edwin R. Sherman. Less than 12 bucks on Amazon. It's geared for marine applications, but the basic 12-volt theory holds for our bikes.