Starting circuit troubleshooting

cliffhanger9

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I have an all original, stock, bought from 1st and only other owner, 1981 yamaha xs650 special

It ran beautifully. Electric start but started within 2 kicks if started that way. One day I was riding and it just shuts off and dies. I coast to a stop. Turn it off. Turn the key back on but nothing comes on despite being in neutral no lights, no nothing.

Battery reads 12v when its disconnected from bike but when connected and turn the key on reads 0 or 1v.
Pressing start button does nothing and bike will not kick start on either in this state.
If I leave the key in the on position and walk away there's a chance some magic has happened and the taillights and green neutral light will have come on without anyone touching anything in my abscence. Check voltage, back to 12v. If i press the starter button, I hear the started solenoid click and the lights go out everytime back to nothing, no voltage reading on the battery.

If the light magically comes back on 5 or 10 mins later, and i kick it, sometimes it will start and runs fine (seemingly, never have taken it farther than around the block because if it were to die again, getting it to start again is unreliable.) But this proves that the mechanics and fuel systems of the engine runs and seems to assuredly be an electrical issue. If I leave it on to idle and check battery voltage while running voltage reads between 13-14v so seems like alternator is running. And after it sitting for a couple months the battery still reads 12v without trickle charge so it seems the battery is heathly. I'm not sure what else to check now. I've unplugged the headlight, and the start circuit cutoff relay and neither of these conditions makes any difference. Any recommendations on what else to try troubleshooting? Friends have recommended check for a loose ground but this is my first experience troubleshooting a DC system as i've never had any issues with this bike before, (first bike) . The battery to frame connection just behind the battery is tight.

Any guidance greatly appreciated.
 

xjwmx

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Don't leave it with the battery reading low or it will kill the battery if it isn't dead already which is probably is, Meanwhile...remove all the fuses from the fuse box. Put them back in one at a time watching the battery voltage and that will help you find where the short is, Once you find what branch you could unplug components in that to zero in further. It is probably something like raw wire rubbing on frame. A battery that will only read 12 isn't good. You should be able to charge it to read between that and 13. But as long as there's some voltage there you can still use it for the troubleshooting since nothing should be yanking it down to 1v regardless

BatteryChart.gif
 
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WideAWAKE

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I’d start with checking all your grounds and fuse connections (I’d pull and clean em if it was mine) , and then your switch. Make sure it passes power through it.

I’ve found sometimes even if a multimeter with chime for conductivity for ground at its pin point it can still be bad and intermittent. The reason to pull and really clean em.
 

5twins

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I'm guessing your battery has failed, gone belly up. How old is it? Many times, when a battery goes bad, it will show around 12 volts at rest but goes dead as soon as you try and put a load on it. You could pull it out, take it to an auto parts store, and have them load test it. Most will do this for free.

When testing the charging voltage at the battery while running, you want to test it at idle and then revved up to around 3K RPMs. 12 to 13 volts is normal for idle but when you rev it up, the output should climb up into the mid 14's. If you get no change in voltage when revving, you have charging issues.
 

xjwmx

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Your reliability concerns in general, we can't see what it looks like obviously, but if it's a bit crusty I'd consider buying a new stock harness for it. It's worth it to not fight connector issues. Keep the old one handy for reference and parts, in fact never throw any of your old parts away. Seems like there's always something you can rob off a bad part and use
 

Jim

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If I leave the key in the on position and walk away there's a chance some magic has happened and the taillights and green neutral light will have come on without anyone touching anything in my abscence. Check voltage, back to 12v. If i press the starter button, I hear the started solenoid click and the lights go out everytime back to nothing, no voltage reading on the battery.
Classic symptoms of a bad battery. Any auto parts store will load test it for free. Take it to one. After they determine it won't pass the load test they'll be more than happy to sell you a new one.
 

Jim

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Meanwhile...remove all the fuses from the fuse box. Put them back in one at a time watching the battery voltage and that will help you find where the short is, Once you find what branch you could unplug components in that to zero in further. It is probably something like raw wire rubbing on frame.
The battery slowly recovers enough so that he can kick it and it runs. Yet if he tries the starter, everything dies. That doesn't point to a short.
If the light magically comes back on 5 or 10 mins later, and i kick it, sometimes it will start and runs fine
Before you get too far into ripping and tearing on your electrical system Cliffhanger, get the battery tested and most likely, replaced.
 

xjwmx

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Leaving it alone with the key ON and it comes back to 12v from 0-1v ("by chance") sounds like intermittent short to me. What does it do if the key is OFF? We don't have enough information. But to find if it's only a bad battery, disconnect a terminal and see what it does to the battery. Also, measure your battery voltage literally at the battery, since a bad connector could have the meter floating, looking like 0-1v.. And make sure you've gone through an FAA approved checklist
 

xjwmx

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Interesting... a short that drives a battery to 0 and never blows a fuse or smokes a wire... and then mysteriously goes away allowing the bike to run.
Must say, I've never seen a short like that. I have however, seen literally dozens of bad batteries do what the OP is describing.
Perhaps you could point the OP in the most likely area a short would reside that's strong enough to drive a battery to zero without smokin' all kinds of shit, disappear like it never happened, then mysteriously reappears when the starter is engaged? One that exactly mimics a bad battery at that.
Hell, never mind the OP, I need to learn about this elusive and exotic short... us FAA types are kinda dim in the ways of 'lectricity... ya know?

You don't. Anyone who's ever left the headlights on overnight in their car has seen a battery act exactly as described and has all the info they need.

Say... ain't we butted heads over batteries before? Something about batteries being able to simultaneously charge and discharge? :rolleyes:
That was you that didn't have a clue what he was talking about... right? :umm:
Dude you are so messed up
 

xjwmx

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That other thread, I made a mistake that I freely admit. Everybody makes mistakes, except you. Think about that
 

xjwmx

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Battery operation is taught the first day in Electricity 101. Yet you failed to grasp a most basic concept.... batteries can't charge and discharge at the same time. "Think about that."
I DID think about that. It's how this top 10 research university physics major came to the conclusion he was wrong about that circuit.
 

Jim

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Deleted my comments that weren't helpful to OP... with apologies.


Untitled.png
 

gggGary

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:twocents:
Remove, wiggle, check the ground strap, a very common failure point, wires corroded/broke/rotted lots of white powder present. Another common issue with older Yamaha fuse boxes; the fuse connectors rot in place no long hold fuses tightly, intermittent circuit connections a symptom. Never hurts to do a battery load test either. ;)
Add in ignition switch contact corrosion the switch sits facing up in weather, water gets in, corrosion results.
 

GLJ

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It could very well be a battery. Also sound a lot like a bad connection. Couldn't count how many times I wiggled battery cables on cars and they miraculously cranked like a fully charged battery was in it. It all starts at the battery so that is the place to start testing. Sometimes there are even 2 or 3 problems going on.
 

Jim

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:twocents:
Remove, wiggle, check the ground strap, a very common failure point, wires corroded/broke/rotted lots of white powder present. Another common issue with older Yamaha fuse boxes; the fuse connectors rot in place no long hold fuses tightly, intermittent circuit connections a symptom. Never hurts to do a battery load test either. ;)
Add in ignition switch contact corrosion the switch sits facing up in weather, water gets in, corrosion results.
All very true. It's been my experience though that something such as a corroded ground strap doesn't usually recover enough to be able to kick start the bike as the PO stated. As a rule, if there's corrosion... you're done... until you fix it. Which is why I suggest having the battery checked first. Seems the most likely.
And I don't entirely discount the possibility of a short, but... there's only one system on the bike that's not fused. The starter motor. Highly unlikely, but the starter could have shorted out internally... or the wire too it.
Having said all that, I'd still have the battery checked first... no? :sneaky:
 

650Skull

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I have an all original, stock, bought from 1st and only other owner, 1981 yamaha xs650 special

It ran beautifully. Electric start but started within 2 kicks if started that way. One day I was riding and it just shuts off and dies. I coast to a stop. Turn it off. Turn the key back on but nothing comes on despite being in neutral no lights, no nothing.

Battery reads 12v when its disconnected from bike but when connected and turn the key on reads 0 or 1v.
Pressing start button does nothing and bike will not kick start on either in this state.
If I leave the key in the on position and walk away there's a chance some magic has happened and the taillights and green neutral light will have come on without anyone touching anything in my abscence. Check voltage, back to 12v. If i press the starter button, I hear the started solenoid click and the lights go out everytime back to nothing, no voltage reading on the battery.

If the light magically comes back on 5 or 10 mins later, and i kick it, sometimes it will start and runs fine (seemingly, never have taken it farther than around the block because if it were to die again, getting it to start again is unreliable.) But this proves that the mechanics and fuel systems of the engine runs and seems to assuredly be an electrical issue. If I leave it on to idle and check battery voltage while running voltage reads between 13-14v so seems like alternator is running. And after it sitting for a couple months the battery still reads 12v without trickle charge so it seems the battery is healthy. I'm not sure what else to check now. I've unplugged the headlight, and the start circuit cutoff relay and neither of these conditions makes any difference. Any recommendations on what else to try troubleshooting? Friends have recommended check for a loose ground but this is my first experience troubleshooting a DC system as i've never had any issues with this bike before, (first bike) . The battery to frame connection just behind the battery is tight.

Any guidance greatly appreciated.

Welcome cliffhanger9,

First off........tell us a bit about the bike, condition, how long you have had it and posting pics helps to solve the problem 90% of the time because it helps us see the condition of things and instead of someone suggesting corroded battery leads, (instead of asking you for diagnostic purposes), pics help to isolate an obvious problem with out a lot of guess work.

A mechanic can see an diagnose on the spot. We are trying to guess the problem from a description, ( and a good one it is), without any visuals or background.

My take is the battery has been drained but not do much it doesn't create a surface charge. Something that hasn't been mentioned is the rotor. These rotors are 3 phase and sometimes one phase will go and it will still charge, but not enough to fully charge. The running bike is drawing power from the battery but the rotor is not crating enough to charge the battery, just enough to stop the battery from draining as fast if it wasn't getting any charge at all.

This would also create the symptoms you describe.

A simple test of the rotor will tell you if has failed. An ohm test across the slip rings should be anywhere from around 4.9-5.2 ohms for it to be working properly. If the rotor is defective it causes the regulator to be open all the time and this can burn out the regulator and also cook the battery.

With the suggestions made, make a list and go through things one at a time to eliminate. Easy things first.
 
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