Headlight and horn doesnt work 2005 yamaha R1

SOURCE: 2005 model yamaha r1 motorcycle

It sounds like you have a poor ground connection. You'll have to disassemble and check the wiring harness for broken wires, start up near the ignition switch or around anything that is no longer stock on the bike (like aftermarket turn signals, fuel nanny, power commander, etc.)

SOURCE: 2005 yamaha r1, the headlights went out

check connections obviously when you came down from the wheelie a connection came lose buddy get back to me if ok

SOURCE: Where is my thermostat on my 2005 r1

Check this ilustration out
http://www.bikebandit.com/houseofmotorcycles/2005-yamaha-motorcycle-yzf600rt-yzf600r-water-pump/o/m8997sch296425
Shoild be where a hose from the radiator, goe into the engine, just behind a small cover, which will require a new gasket as well.

SOURCE: The horn on my R1 sounds like a cat crying! The

Low level on battery, or no charging. How strong are your headlights?

SOURCE: 1978 yamaha dt250

MAKE SURE THE BATTERY IS IN A GOOD STATE OF CHARGE, ON THE OLDER BIKES WITH AC LIGHTING THE BATTERY ACTS AS A RESISTOR, HENCE IF THE BATTERY ISOLD AND NO LONGER WORKING, WHEN YOU RUN THE MACHINE ALL THE BULBS WILL BLOW, STARTING WITH THE NEUTRAL LIGHT, AND SO ON, AS THE BRAKE LIGHT , HORN , AND INDICATORS ALL WORK ON THE DC ELECTRIC SIDE IT WOULD PROBABLY BE A GOOD IDEA TO CHECK YOU ARE GETTING 6VOLTS FROM THE BATTERY TO THE IGNITION SWITCH, YOU COULD LOOK FOR BROKEN WIRES AROUND THE HEADSSTOCK AREA, OR CORRODED BLOCK, AND OR BULLET CONECTORS ALSO IN THE COMPLETE HARNES.