Topic: 750 K0 electrical demons!!

[Tews19]

Well today I tried to hunt down my electrical gremlin on my K0. I have 12.74V to everything upto my ignition switch. Then when I try to see where a break is, nothing. It's all testing out properly. I used my new repop Yamiya controls and it worked fine. Then a pop.... Sounded like the fuse blew but it did not...

I grabbed the old control and nothing, no power at all still.

I pulled the ignition switch itself, tested for Ohms and it came back functioning properly.

Any help would be greatly appreciated.

[Spanner 1]

With the Red +probe of your meter on the ign. switch Red and the Black meter lead on the battery Ground you read 12+V right ? With the headlight turned on first, what happens to that voltage when you turn the ign. 'on' ?

[Tews19]

With the Red +probe of your meter on the ign. switch Red and the Black meter lead on the battery Ground you read 12+V right ? With the headlight turned on first, what happens to that voltage when you turn the ign. 'on' ?

Yep, just as you stated Spanner that is correct. I have no power at all after the ignition switch itself. My gauges won't light up so i havent tried w the headlight. Also the horn amd turn signals do not work now

[Spanner 1]

Bad ign. switch or ( my bet ) loose and corroded main fuse clips. They must be tight and grip the fuse to where you can't pull the fuse with your fingers !.. also must be completely shiny for electrical connection 

[Don R]

 You can plug a blade fuse onto the wires on a k0 fuse panel. Try that.

[Tews19]

Bad ign. switch or ( my bet ) loose and corroded main fuse clips. They must be tight and grip the fuse to where you can't pull the fuse with your fingers !.. also must be completely shiny for electrical connection 

I literally swapped out a fuse block from a 69 750 and it works perfect. Tried  it again and samerhing. Nothing. I put my fuse block on the 69, full power there.

[pjlogue]

Water ingress into the ignition switch can cause corrosion which in turn can cause heating which can melt the solder where the wires connect to the switch.  Take the switch apart and clean any crud out and remove any oxidation from the contacts inside the switch.  To open the switch you need to bent the crimp dimples out.  Be careful not to lose springs, BB's when it comes apart. 

If you have corrosion there you will have it in other areas of the harness connections.  The output from the alternator is a particular concern.  A lot of bikes have the connectors over heated from corrosion on the terminals.

-P.

[Tews19]

You can plug a blade fuse onto the wires on a k0 fuse panel. Try that.

I swapped the fuse single box from a 69 750, it works on the 69. That's not the issue. It's freaking mind boggling.

[Tews19]

Water ingress into the ignition switch can cause corrosion which in turn can cause heating which can melt the solder where the wires connect to the switch.  Take the switch apart and clean any crud out and remove any oxidation from the contacts inside the switch.  To open the switch you need to bent the crimp dimples out.  Be careful not to lose springs, BB's when it comes apart. 

If you have corrosion there you will have it in other areas of the harness connections.  The output from the alternator is a particular concern.  A lot of bikes have the connectors over heated from corrosion on the terminals.

-P.

P, on my stator, i had to repair one of the three wires.  Are you saying my stator could be the culprit for absolutely no power after the ignition? How can i test my stator?

[bryanj]

If you have 12v at the red switch wire but 0 on the black with switch turned on switch is bad. Temporarily connect red to black in loom connector block with a jumper wire if all works proves switch duff

[Spanner 1]

^ Brian+1...….. you can make a jumper wire from the battery + to the Black wire on the regulator ( has B/G/W connections ) right below the battery = bypassing the ign. switch and saves you from removing the tank to get to the ign. switch connector 

[Tews19]

If you have 12v at the red switch wire but 0 on the black with switch turned on switch is bad. Temporarily connect red to black in loom connector block with a jumper wire if all works proves switch duff

I removed the brown encasing on the switch and also on harness. I trimmed the M and F ends off and have exposed wires. I made jumpers from red to red off the ignition  and the black, brown and brown/white wires. 12.74V to everything.

[Spanner 1]

And what happened ?
Does the bike start and all the lights work ?

[Tews19]

12.7v to red to red, black to black, brown to brown and b/w to B/w.

[Spanner 1]

 ^

[Tews19]

And what happened ?
Does the bike start and all the lights work ?

Nothing, no power, no lights. I can't even jump the solenoid

[Spanner 1]

If the starter wont turn when you 'jump' the big terminals on the solenoid, then I'd be having a close look at the battery terminals. Need to be tight and the surface of the terminals must be shiny bright.  Also the top of the battery's terminals shiny. Good luck !

[Bankerdanny]

If bridging the solenoid terminals does get it to turn over then I would check the ground connection and the connection from the positive terminal to the solenoid.

[HondaMan]

The K0 has a bullet-contact type main plug on the power switch, and those contacts are only rated to 15 amps. After 50 years, they won't carry 10 amps, as they were not even plated with zinc(!). Unplug the main switch and check the condition of the contacts: they are likely burnt. I have the K2 with the same switch, now the 4th one. I finally changed it to be the later version, with the blade contacts instead of the bullets, and since they are rated to 17 amps, it has not had any more trouble in the last 10 years from it. If you need the mating connector to add to the harness, go to www.vintageconnections.com and get the 4-blade connector set (about $5) and their excellent crimpers. I also add a dab of solder to that joint, as the solder improves the conductivity about 15% more.

[Tews19]

If bridging the solenoid terminals does get it to turn over then I would check the ground connection and the connection from the positive terminal to the solenoid.

Jumping did nothing unfortunately Dan.

[Tews19]

The K0 has a bullet-contact type main plug on the power switch, and those contacts are only rated to 15 amps. After 50 years, they won't carry 10 amps, as they were not even plated with zinc(!). Unplug the main switch and check the condition of the contacts: they are likely burnt. I have the K2 with the same switch, now the 4th one. I finally changed it to be the later version, with the blade contacts instead of the bullets, and since they are rated to 17 amps, it has not had any more trouble in the last 10 years from it. If you need the mating connector to add to the harness, go to www.vintageconnections.com and get the 4-blade connector set (about $5) and their excellent crimpers. I also add a dab of solder to that joint, as the solder improves the conductivity about 15% more.

I bought the their kit w the crimper tool. Excellent stuff from the company and I highly recommend them. Excellent customer service too.