Well, I just finished installing the Stebel Air Horn on the M50, & I took a few pictures that might help you out. Thanks to all those who posted instructions before me, I found them extremely helpful, however very little pics. I also recommend using the instructions that come with the horn itself. Here is what I did:
1.- Make sure your tank is pretty much empty, you do not want to have to move a full tank of gas.
1.2.- I fabricated a bracket out of a 4" piece of alluminum, drilling a few 8mm holes. These come in helpful if you do not want to do much measuring when installing the horn itself.
1.3.- Remove your PAIR valve cover, we will use one of the existing screws to mount the horn.
1.4.- Remove this long screw & install the bracket here. Tighten the screw, & place the PAIR valve cover back on loosely. You will need to check for fit, so the horn does not rub up against the cover. With the cover on, test to see which hole on the bracket you will need to mount the horn on.
1.5.- Here is the horn in place. IMPORTANT: Make sure you mark or remember which is your hot & ground on the horn! You do not want to be looking under it upside down later. I opted for removing the horn to take a look when I was ready to wire it up.
2.- Remove Both seats & loosen gas tank. You might be able to get away without moving the gas tank, I just did it to keep a clean installation when running the wires along the frame.
2.1.- Remove the neck cover on the left side of the bike. It should come of pretty easily with a tug out & up. Here you will unplug the old horn, no need to remove it at all or cut any wires, you can use the existing connector using a couple of male spade connectors.
2.2.- Run your wires along the frame, I used zip ties to thread it along where other wires or tubes are. This I leave at your discretion, depending on the length of your wires, and how clean of a job you want to do.
2.3.- You can pretty much drop in the relay in the FL corner of the battery, leaving all your connections readily available. It is tight enough where it will not move. You are now ready to make your electrical connections. Here I will leave you with the supplied instructions, as I have reached the limit on pics I can post, & they are self explanatory as to what goes where.
2.4.- Another important note: Test the horn before putting the bike back together!!
2.5.- THIS THING IS EXTREMELY LOUD ! !
If you have any questions or want to see a few more pics, let me know.