Arc, Lights, but no starter or horn

While getting my 1971 R75/5 ready for the season, I accidentally arced the hot side of the battery to the frame. Now I have all lights, but it will not turn over and the horn doesn't work. This was after a long cold winter of storage. Any ideas of what I should check first. Would the diode board keep it from getting power to the starter? Any help would be greatly appreciated.
Thanks,
Tom Anderson
thomasmanderson@windstream.net

System

OKAY short answer. the diode board has nothing to do with the starter circuit. Do you see any obvious damage to wiring? Did you see any smoke in the harness or wiring when you touched the battery to the frame?

So, when you try to start does anything at all happen? For example do you hear any clicking, or slow cranking noise? What is the battery voltage, how old is the battery? Did you have it on a charger? Can you get someone to take a voltage reading at the battery terminals with the bike sitting, then, take a reading when you turn on the key and hit the starter button. What is the difference between the two reading? First thing to check is if the battery is good.

Anything after that would require a visual inspection for damage to the wiring either from the short or rodents. The only other troubleshooting will require a good wiring schematic and the proper test meters, and a test light. With a schematic you can break down the ignition circuit and starter circuit to check them.

Where are you located? St.

Welcome to the forum! Usually when I see someone has lights, etc., but no starter, I go to the starter relay. Something that's easily checked.

Could Be

Yes, one of the wires from the positive side of the battery does sometimes go to the starter relay. Could be the arc fried the relay. Does your bike have fuses or not. Looking at what schematics I have on hand for R75/5 without fuses, there is a direct link to the starter relay. From there, a red wire goes to ignition and light switch, from there, to the headlight dimmer switch.

I also sadly see a direct line from the battery to the rectifier.

So, you have a job ahead to inspect for burned bits in this redline path. Good luck. St.

Thank you!

Thank you to everyone who replied! Yes, I have the /5 with no fuses. Battery was fully charged and checked.
After reading many posts, I went back into the garage and gave it a kick to see if it would fire like some posts said it might.
It fired enough for me to know it was getting spark. Well, I hit the starter button, and it turned over like it should!
I can't explain what was going on. And yes, when I hit the starter button, there was nothing, no clicking, chirping or anything....just silence. Same with horn.

Anyway, I'm very happy that I got to go out and ride the rest of the day. I also have a 2018 R1200RS, and would have a very hard time choosing between the two if I had to choose.
They both have their positives, but my 1971 R75/5 just has this SOUL to it that the 1200RS is lacking.

Only on an airhead

LOL, oh man, I am so happy your problem was simple and it is working now like it should. I have seen shorts like you had do a lot more damage, not on bikes but on cars from back in the day when I wrenched. I could tell stories but won't bore everyone.

So, as to why the buttons wouldn't work who knows? Perhaps a well placed shot of contact cleaner into them might help? LOL, I wouldn't mess with taking them apart until they fail, you might be able to squirt some cleaner in.


I have never ridden anything but airheads, and a couple of the first edition of the K bikes a long time ago. I do have two variations on airheads and agree, choice is very nice! Glad the problem is solved and you told us the outcome. I am going riding in a bit, have fun if you do as well. St.