2003 Onwards SR400 Wiring

From 2003 onwards Yamaha introduced a new key/ignition unit for the SR400, changing it to a coded key the same as the rest of their line. When purchasing a new SR400 you'd receive three keys, one of which was the red "master" key. Only this one could be copied.

Each key contains a chip in it, which is matched to the arial which surrounds the ignition barrel. Only the keys issued with the bike will match the ignition system. Others may fit, probably even turn the barrel but a red LED that sits in the speedo will stay on. No matter how hard you kick it, she won't start.

If you lose all the keys there's no option but to replace the whole unit - I've seen them go for around $500AUD on Yahoo auctions but the system new from Yahama costs a few thousand dollars. So don't lose your keys.

Anyway, while having some problems with the ignition system I contacted a friend in Japan who hunted down these diagrams for the late model wiring system. They might come in handy for ordering replacement parts and/or stuffing about with the electrics. It's also yet another reason to learn Kanji, if dirty Hentai magazines weren't enough.

If it's any help, the arial has to sit directly around the barrel for it to work. Just in or out or around won't. I stuffed around, and stuffed a friend around for quite a while before we realised that it didn't work.

2003 SR400 Wiring Diagram
Wiring Diagram

Ignition System
Ignition System

Other Stuff
Other Electrics



  1. Hi,

    Was looking at your site, nicely done and very informative. Could I ask you, what kind of battery you are running in the SR? From the picture, looks like a laptop battery, thin and longer.


  2. G'day Don!

    That's the standard SR400 battery now. I think it's the same as some other Yamahas as well - TTR110's and similar. Not a bad little unit. Small and pretty light, but disturbingly expensive.