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Out riding Saturday night and the bike went electrically dead while riding. Checked fuses and battery, all fine. So i got the bike shuttled home and started to investigate.

12v to the switch was good, no power after switch. I have a replacement ignition switch from z1 already in my parts bin so I swapped that quickly and the bike started right up. 

My bike had the factory ignition switch still from 1977, would you imagine this to be just age related or is it possible my led headlight was running too much power through the switch and burned it out? During some free time today I need to sit down with the bikes wiring diagram but I believe all power goes through the ignition switch

I'd rather not swap a new ignition over and have this problem again. Any thoughts for running a relay? 

Dan77Kz750 I suspect if it is the original switch you are replacing (they where marginal at best from new) then you have done well. LED lights draw significantly less current than conventional bulbs so your LED headlight may have helped pro-long the life of your switch 

Thanks, that's was I was thinking but needed to hear it from someone else I think. Being none of the wiring showed any signs of overheating, no fuses were blown, everything works fine with new switch, I'm guessing it's just age. Definitely the original switch, key matches the locks. 

Just gonna post a pic of the specs of my led headlight for confirmation, been on there for a year without causing issue but I do know it's listed as higher wattage than the stock

 

The specs are deceptive, it shows an equivalent (75w) power but doesn't show current draw, however it is widely recognised LED draws significantly lower current. 

Again, that's what I thought but without the specs for current draw and adding that I don't own an ammeter so I couldnt be sure. Appreciate the help. 

The forty year old solder in the switch is likely brittle and can break without notice. As Wookie58 mentioned, the actual switch mechanism was marginal when new and forty-odd years of vibration and use has not improved that. Although, to call an electrical switch that worked flawlessly for four decades marginal, is perhaps a bit unkind.

Exactly, at 45yrs old that poor switch owes me nothing. 

Are they z1 replacements considered to be a better product than the stock unit being it was considered marginal in its time?