Hey all, my 919 led an extremely interesting life before getting to me, and along the way I learned what is, I think, the easiest way to re-key the bike. This is for the North American model, which has a security system reliant on a Zener diode which is usually in the ignition. There are a ton of '919 key sets' available, meaning a tank cap, ignition, and the rear seat latch, BUT! they are nearly all based on the Asian and EU version of the bike, which does not have that system and thus doesn't have a diode. The tank and seat latch for these kits will generally work fine, subject to caveats below, but the ignition will refuse to start the bike. You'll get an FI light, no fuel pump priming, no error codes, and the bike won't go. So:
1. Which keyset to buy? I actually went through a few learning how to do this, but they're cheap. The only thing you need to care about here is the shape of the rear latch. Some versions of the Hornet had a slightly different rear latch that won't work reliably on most US models. The one you want looks like a small triangle, as per the attached image.
2. Add the proper base, or wire in a diode. The ignition base you got almost certainly doesn't have the diode in it. Opening up the base, you will likely see 4 wires, none of them pink. It'll probably look like this, though without a diode in yet.
Your board at the back of the bike is looking for a certain voltage drop from the ignition to make sure it's not hotwired. A new ignition will not do this, so the bike won't start. To fix this, you can either just order the proper ignition contact base from Partzilla, part number 35101-MCZ-670
, or you can solder in a diode.
2.a. If you just ordered a new contact base, it's plug and play. Disassemble the ignition, making sure to keep the stupid springs within contained. You only need to take apart the butt section, and swap it with the new base plate, which does have a pink wire coming out, and a diode already in place.
2.b. If you're cheap and/or like frustrating welding jobs, the diode that you want can be had for 30 cents plus shipping from the good folks at Mouser, here
. Don't pay the absurd markup some people want for these things. The diode can be soldered in either right into the ignition, as in the image above, or you can put it in right next to the board.
The wire you want on the board is, appropriately, the pink wire. It's ECU Gray connector pin #19, and all it wants is to see a voltage lower than battery. I've verified that at least my bike is fine with a voltage as low as 8.5v. If it's 12v or up, the bike won't start. To put the diode in, cut the wire, connect at both sides either with some kinda crimped connecter or solder, and make sure to have shrink tubing over the whole thing. If this connection comes lose, or a crappy connection zaps the diode, you now have a very pretty paperweight until you fix it.
That's it! Now a rescued franken-bike on several keys can be run all on the same key, for either about $80 if you ordered from Partzilla, or ~$30 if you ordered the diode from Mouser and did the pain in the ass soldering yourself.