@#*^%$....bike died...no power...no idea.

Oh this f-ing bike...

I took off on my bike today because it was such a nice day.

I made it maybe a mile, mile and a half from my house, I was doing 60 mph, and the bike just shut off.

I coasted to the side of the road and found that the bike was acting like the battery was disconnected. The key was on the start position but nothing was lit up. I double checked the shut-off switch and it wasn't switched off. Checked all the fuses, they're good.

I pulled the side cover off and jumpered the starter relay with a screwdriver, and the bike will crank like that, but it doesn't start.

I have no clue what happened, not sure if it's a short, or what. What do I need to look for?

Had to walk all the way back home, and now I have to figure out how to get the bike home. Yippee.

I pushed my 79 750 twin back home, but I was only a mile away

IIRC, the main power wire is attached to the solenoid terminal, the same terminal that the battery wire is hooked to. My guess is that the wire has come off the soledoid, or maybe somewhere between there and the fusebox.

"the bike just shut off." as you assumed, blown fuse was a good thought.

Now, regarding "Checked all the fuses, they're good.", I assume you verified by using a DVM for continuity, correct?

With a DVM in measuring continuity (with no power on) or voltage (power on), you should be able to easily trace where the problem is...

I don't have a wiring diagram for your bike so sorry, I can't offer any help there. If you can provide, I'll see where I can help.

OMR

I VISIBLY checked the fuses...mind you, I was on the side of the road while doing this. Didn't even get the bike home until 6:30 PM.

Perhaps I should add, the bike did this one other time...I had it outside my garage, started it and it ran for about 20 seconds and shut off. I looked all over, couldn't find anything, tried it again a few minutes later it was fine and had been fine since (that was about a month ago).

I won't be able to get to it again until Monday evening sometime...given what I've found already, can I isolate this problem to a particular section of wiring, i.e. since there's obviously power getting to the starter relay, it must be somewhere between there and the ignition key?

I'll have to see if I have a wiring diagram in my manual.

The Factory Service Manual for the 750 twin has a wiring diagram in it.

Just checked, red with white stripe from the solenoid to a 20 amp fuse in the fuse block, then white from that fuse to the ignition switch. Check fuses with a multimeter as they can appear good visually while being bad.

Need to find the bad connection and fix it, or it "will" happen again.

This happened with my kz650b. I traced a short inside the electrical wrapped wiring harness under the tank. It was a the main power wire(white I think) and was corroded beyond belief. I re-spliced it and have never had trouble with it since. It was on the left side under the tank, as you ride the bike. Worth checking.

This is the only part of the wiring diagram I could find...

As can be reviewed in the attached image...

From the positive +12Vdc battery terminal, this is fed into connector 4P via conductor color white/red stripe.

Place your DVM (digital volt meter or volt meter for that matter) where the meters black lead is connected to battery ground/frame ground. With the meter set to Vdc and place the RED lead and measure Pin 1 connector 4P, it should display +12Vdc. (NOTE: Assuming battery is charged to ~ +12Vdc). Measure battery voltage, this is what you should see except through diodes in which case subtract .7V from battery voltage.

This is fed to the 30amp fuse as well as pin 8 on connector 4P. You should measure +12Vdc at both these locations.

Pin 8 white conductor feeds into ignition switch connector 6P. You should measure +12Vdc here as well. Switch on your ignition switch and you should measure +12Vdc on the switches brown conductor. This is terminated to connector 18P pin 10, measure +12Vdc there. This feeds into the main relay.

Presuming the main relay is indeed grounded, it should switch, hear a clicking sound when the ignition switch is switched?

When this occurs, the 30amp feed into the main relay is then passed onto the 10amp fuse.... Measure +12Vdc there?
This is then passed onto the main head light relay...

Speaking of which, do you have headlights when the ignition switch is activated to on?

This should provide you a method to trouble shoot your electrical problem.

Unfortunately, I don't have the whole diagram but if you follow the same method, you WILL find your problem.

OMR

Old Man Rock wrote:

Speaking of which, do you have headlights when the ignition switch is activated to on?

Nope...that's what I'm saying. Turn the key, I have no headlights, no "neutral" light, no oil pressure light, no brake light indicator, nothin. The current is getting cut somewhere between the battery and the ignition switch.

I'll pull the tank off tonight hopefully, look over the wiring, and do some testing with a multimeter.

"The current is getting cut somewhere between the battery and the ignition switch"... Not necessarily so.

The open can be all the way to the head light relay via the main relay and 10amp fuse... Actually beyond that even.

Volt meter measurements as described and you'll find the problem... Be patient, take your time, insure you have good grounds and you'll find it, we promise! Electrical is not that difficult if you understand Ohms law and have a volt meter.

Let us know what you find in your trouble shooting.

OMR

two dumb questions,, the kill switch on the bars, it has not been moved or possibly bad.
also does the bike have a kill switch on the kick stand or a clutch in switch.
I dont know about the sepcific bike, just asking

Make sure the fuse connections are clean.
Take some scotch-bright to them,and make em shine.
Wiggle the keys in the ignition.Flick the killswitch back and forth a few times.Kick the tires good and hard.(but don't knock the bike over)

Start with that,and see if it makes a difference.:huh:

OMR, I don't know what bike that diagram is for, but it's certainly not for the bike being discussed. According to his sig it's a 1978 KZ750B3, a 750 twin.

Yes it has a clutch switch, but the clutch switch just works on the electric starter circuit.

No, it does not have a kickstand switch.

The shutoff switch on the right switch pod shuts off ignition and starter circuit, not the lights.