1975 XS650 dies after 10 minutes warm. Doesn't start until next day

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larrynyc

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I recently got a stock 1975 XS650 B. It's in pretty good shape; it's not a basketcase. Brand new AGM battery, cleaned carbs.

The other night, the bike died on me in the middle of traffic. The start button did nothing at all. I parked it and took the subway home. The next day I thoroughly cleaned the kill switch contacts and put in a brand new fuse just in case (this bike only has 1 fuse). I made sure the kill switch contacts were nice and shiny. Voila, the bike started, so I rode it home. I *almost* made it home...

The bike died again a few blocks away from my home. I tried kickstarting it, no good. The start button did nothing. I gave up, left and came back an hour later. I cleaned the start button contacts, very thorough. It worked, the bike started right up. I managed to get home before it died. It won't restart. Kicking has no effect, and the start button makes no sound at all. The headlight is fine, the start button doesn't even dim the headlight.

So I yanked out the left voltage regulator and the relay on the right. I cleaned the contacts on them that evening. The next day, I put them back. Press the start button, the bike starts! Ran nice and strong, without a hitch. So I let it idle a good 5 mins and then take off. My smile ended about 3 minutes later, because the bike spontaneously dies about a quarter mile up the avenue. No sputter, just suddenly shuts off, and I coast to a stop. The same symptom--headlight is fine, but no effect from the start button or kick. I walked home.

Does anyone know what's going on? I am 95% sure it's electrical but I don't know where to look. Thanks
 
nj1639 said:
If it were mine, the next time I had it running I'd check the headlight and see if it brightened up when given a bit of throttle. Could be that battery.
Click to expand...
Thanks for replying.

Normally I'd agree with you, howver I literally just got a new AGM battery three weeks ago, and the night before the last attempt I brought the battery home to charge it on a digital BatteryMinder tender, and it's fully topped up. I'm very certain it's not the battery. This is why it's so puzzling.
 
Check your charging system with a volt meter. Should be putting out about 14-14.5 volts at 3000 rpm at the battery. Plenty of info on the site about troubleshooting if it's not working. Have your battery load tested, just because it's new doesn't mean it's good.
 
Larrynyc, if an engine cuts out like that I have a mental check:

1. Is the fuel getting through? (dirt from the tanks does all kinds of things to the carb function - I have just got an inline filter)

2. Is the battery charged - yours is charged, but is it charging while riding?

3. Whats happening in the cylinders - pull the plugs and what are the plugs showing? (cut-out can be caused by a false-earthing [grounding] with a build-up of carbon or oil or even excess fuel on the plugs)

You're pretty sure about the battery, there is some fuel getting through to start up, so let us know the condition of the plugs.

Anlaf
 
Thanks guys, I really appreciate everyone's input.

I put new in-line fuel filters in a few days after I got the bike. But that doesn't explain why the start button ceases to work (zero effect at all when pressing it, no sound, no dimming).

But, ANLAF, your comment about the charging, as well as nj1639's and Grinder's comments got me thinking.

Here's a little more background: When I got the bike approx 2 months ago, the previous owner said he just put in a new battery. It looked pretty new. I charged it up with the digital tender to make sure it was all good. About a month ago, the blinkers started acting funny when I revved the engine--if I had a turn signal on, the signal would flicker erratically when above idle, then return to normal flashing at idle. I thought the seller swindled me about the battery, so I bought a new one. New battery . . . blinkers still did the same thing. Hmm, I thought perhaps the turn signal flasher was going bad. No big deal, I haven't gotten around to replacing it, because the bike ran fine. Ah well, I have 2 batteries now.

But now it seeming more and more like the charging system.

I will report more when I get to the bike again. It's on a city street curb about a mile from my place so I have to walk there after work. I have the other battery on a tender right now, I'm going to swap it out to see what happens.
 
larrynyc, are you still on the stock rotor/stator?

If you are you:
1. check the funtionality with a multimeter
2. check the brushes are not worn
3. can clean up the rotor surface
4. clean connections including earth/ground.

Anlaf
 
Last night I worked late, so I could only get to the bike at night. So I decided to just get the bike home, and do the recommended tests at a later time when I had easy access to my tools at my place.

I figured, with a fresh battery it should last the 5 minute ride to get home. I trickle-charged the other AGM battery (which was a different brand, and only a few months old) overnight, so it was fresh and ready to go.

I swapped the battery with the brand-new charged battery. I pressed the button -- the bike started nice and strong. After warming up about 2 minutes, I rode it for about 30 seconds, and it started bogging and then died. The start button was then unresponsive. Kickstarting did nothing. I smelled a subtle electrical burning smell.

I pushed it a mile home and went to sleep. I'll try the tests you recommended, and will report what I discover. Many thanks.
 
Update:

So I discovered a few things went wrong at the same time:

* The plugs were *heavily* fouled with carbon. I'm surprised they worked at all. This caused a false ground when warm.

* One plug wasn't firing. This caused the bike to be more prone to dying.

* The plug lead cables were haphazardly installed, and some of the grousing leads were dirty. This is what caused the left plug not to fire.

* And initially, the start button and kill switch were both dirty.

* The idles were un-synced and the fuel/air mix screws were different.

* The cable from the battery to the solenoid was old.


So I cleaned the kill switch, cleaned the start button, sanded and gapped the plugs, snipped and re-attached the plug lead cables, turned the mix screws to both 3/4ths out, I dead-synced the carbs individually then made the idle 1200rpm, I swapped out the battery cables and put brand-new ones.

So.... The bike started and ran strong! I rode it around for 20 minutes....

And then it died. I pressthe start button, nothing. No response.

Now I have to note, there's *no sound at all* when the start button is pressed. Earlier (when the bike worked) I did a test and the starter would still churn even without the spark plug wires hooked up at all, so it's not the coils causing it to not be responsive.

I'm out of ideas
 
Hello,

Ah yes I did the fuse as well.

I have a new set of 20AMP fuses, my bike year uses only 1 fuse for the entire bike. I tried two just in case.

I just tested the battery, it's at 12.5 volts right now after being unused for about 5 hours.

I just let the bike cool for 4 hours and it's not working.

An old guy walked by me on the sidewalk, and said "It's the relay" and walked away. Could that be the case?
 
Larrynyc, what you've described is a faulty/intermittant power supply to the coils, flasher unit, and starter solenoid energizer line. On the other side of the fence, you've said the headlight still works. While it's dead, check the flashers, taillight, brakelight, and horn. What this will do, is help to identify where in the wiring harness a break or bad connection may exist, in the brown ignition supply line.
 
larrynyc said:
Hello,



An old guy walked by me on the sidewalk, and said "It's the relay" and walked away. Could that be the case?
Click to expand...

yes :D it could very well be the safety relay but my money is on the starter solenoid switch.

Does your bike have the yellow cable from the alternator connected to the safety relay ? some disconnect it and the safety relay.
The yellow wire senses when you're engine is running and disconnects the safety relay thus preventing your starter working when the engine is turning.

The fault could lie somewhere in that circuitry I suspect so you need to look for a schematic in the tech section and fault find.

As a tempoary measure you could try disconnecting the yellow wire and disconnecting and bypassing the safety relay
 
Last edited:
Grinder said:
Check your charging system with a volt meter. Should be putting out about 14-14.5 volts at 3000 rpm at the battery. Plenty of info on the site about troubleshooting if it's not working. Have your battery load tested, just because it's new doesn't mean it's good.
Click to expand...


Have you done this check? 14-14.5 volts at 3000 rpm at the battery.
 
peanut said:
yes :D it could very well be the safety relay but my money is on the starter solenoid switch.

Does your bike have the yellow cable from the alternator connected to the safety relay ? some disconnect it and the safety relay.
The yellow wire senses when you're engine is running and disconnects the safety relay thus preventing your starter working when the engine is turning.

The fault could lie somewhere in that circuitry I suspect so you need to look for a schematic in the tech section and fault find.

As a tempoary measure you could try disconnecting the yellow wire and disconnecting and bypassing the safety relay
Click to expand...


Yep, I had fits with this some time ago.
 
nj1639 said:
Yep, I had fits with this some time ago.
Click to expand...

its a tricky one to diagnose as there are so many components that could be implicated :D

It sounds like there may be more than one issue here .

Certainly the starter motor isn't turning over so that can be troubleshooted fairly easily.
I'd run a jump wire from the battery straight to the starter motor and flash the terminal. If the starter turns over that should eliminate the starter motor being faulty or jammed straight off.

Then I'd check that I had 12v+ at the starter solenoid switch.If not I'd check the L/W (blue white)supply wire from the start switch and bypass it if it was open circuit.

Once I had a 12v+ supply to the solenoid I'd then disconnect the safety relay and run a jump wire from the other side of the solenoid to earth and that would check the solenoid operation.

Then if that checks out you'd be looking at the safety relay and kill switch etc. Its just a process of elimination. Easy when youre at home in the armchair ! not so easy out on the street ...:wink2:
 
Thanks guys. I feel like we're zeroing in on the culprit for sure. The thing is I am a NYC rider so I have no car, and I have no garage. My tools have to be carried downstairs three flights every time I work on the bike (and I can't leave my tools at the bike unattended because they'll be stolen!) Also, I can only work on the bike during the daylight hours, and when it's not raining. My bike right now is about a mile away (I make sure to test it within a mile so I don't have to walk so far). All this, and a dayjob during most sunlight hours, and a lady who demands a lot of attention, is making my progress really really slow, ha. Plus, half the time I'll walk all the way to the bike and realize I forgot my multimeter. Or a spark plug socket. Or my key!

Anyway, I'll report further findings in the near future. I feel we're close. Thanks to all again.
 

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