wanted to share a fix i completed tonight for anyone that has a bike with a missing start button. i'm really green when it comes to wiring so it took some time for me to grasp how it works and which momentary switch i would need. for my 750 k6 i needed a switch with three terminals. normally open, common and normally closed. could be similar on other models but not sure. on the 750 k6 there is a yellow with red stripe (for starter solenoid) that connects to the normally open terminal. black (+12V) that gets connected to the common terminal. then a black with red stripe (headlight) that gets connected to the normally closed terminal. in the photo below you'll see the switch terminals are labeled. NO, C, NC. additionally my headlight would not turn off when i pulled the headlight fuse. with a tip from madmtnmotors in an old thread
http://forums.sohc4.net/index.php/topic,164462.msg1901548.html#msg1901548 i was able to find that the brown with red stripe wire that runs from the fuse box to the left hand control was moved from it's mate to a black (12+V) in the headlight bucket. rectified that and with the fuse pulled the headlight shuts off and also when pushing the new start button the headlight goes off temporarily as it should.
i got the switch from
https://www.surplussales.com/ for a few bucks so i bought 4 to make the minimum purchase. it fit well into the right hand control however i found trimming the long terminals down a bit made it easier. the button itself sits a bit proud but it doesn't bother me.
