Weird behavior after engine start

[m00shu]

I've been able to find the answer to most of my questions here. However, this one has me stumped:

81 XS650S

As you can see, bike is starting fine. Runs for a bit then shuts off. I'm not touching anything after the bike starts. Then after a bit it comes back to life and I can start again.

From what I can tell it seems to die faster when the bike has warmed up.

This is a new problem that hasn't always existed.

Things I've done:
New harness
Verified batter is good.
Voltage is good at 2.5-3k rpm
Removed all unnecessary items and same issue
Replaced all fuses
Same behavior if hooked up to charger

 

[Bucko]

I would take a guess at a faulty coil,they break down as they warm up if faulty!

 

[ANLAF]

Bucko could well be right, of course. Down to the two main possiblities, fuel supply or ignition. No hint of poor running then cuts out, hmmm! What charging system do you have, and what jets and float height? Do you have the starter safety relay operating. sounds like a cut-off and start again as if nothing had happened. Is it the same few seconds gap from cut-out to ignition light?

ANLAF

 

[TwoManyXS1Bs]

It acts like a faulty self-resetting circuit breaker in the main line that's overheating.

 

[5twins]

I'd definitely be looking at electrical stuff the way it kills all the lights too, then comes back on in a bit. Do you have a sidestand safety relay?

 

[XSLeo]

Did you check for spark as soon as it quits?
Did you open the gas cap as soon as it quit? Hear air wooshing into the tank?
If you have spark when it quits then the ignition/electrical side is probably ok.
If air wooshed in it could be a vacuum build up in the tank restricting fuel flow. Check the vent in the cap.
www.amckayltd.com/carbguide.pdf will help with carb issues.
Leo

 

[5twins]

Yes, but if it dies due to fuel issues, I don't think all the lights would go out. This thing is quitting like the key was turned off.

 

[retiredgentleman]

Run a temporary wire from the battery positive terminal to the ignition coil red/white wire. Start the engine and see if it keeps running.

If it keeps running, you have narrowed it down to the main fuse, ignition switch, ignition fuse or the kill switch.

Then you can by-pass each one of those 4 to see which is faulty.

 

[m00shu]

I would take a guess at a faulty coil,they break down as they warm up if faulty!

Checked the ohms on the coils and they are reporting the correct values.

Bucko could well be right, of course. Down to the two main possiblities, fuel supply or ignition. No hint of poor running then cuts out, hmmm! What charging system do you have, and what jets and float height? Do you have the starter safety relay operating. sounds like a cut-off and start again as if nothing had happened. Is it the same few seconds gap from cut-out to ignition light?

ANLAF

I think I have the stock charging system. Is there an easy way to check?

I tried tracing wires all over on the bike and could not locate the safety relay. Unless it's inline on the harness. Where should it be located?

The time varies I'm not able to lock down a set amount of time.

It acts like a faulty self-resetting circuit breaker in the main line that's overheating.

Is there a self-resetting circuit breaker in the harness somewhere?

I'd definitely be looking at electrical stuff the way it kills all the lights too, then comes back on in a bit. Do you have a sidestand safety relay?

Not that I could find.

Did you check for spark as soon as it quits?
Did you open the gas cap as soon as it quit? Hear air wooshing into the tank?
If you have spark when it quits then the ignition/electrical side is probably ok.
If air wooshed in it could be a vacuum build up in the tank restricting fuel flow. Check the vent in the cap.
www.amckayltd.com/carbguide.pdf will help with carb issues.
Leo

I'm able to kickstart while it's 'off' before the lights come back on though not all the time. No wooshing air.

Run a temporary wire from the battery positive terminal to the ignition coil red/white wire. Start the engine and see if it keeps running.

If it keeps running, you have narrowed it down to the main fuse, ignition switch, ignition fuse or the kill switch.

Then you can by-pass each one of those 4 to see which is faulty.

Tried this and still have the same issue happening.


New developments:
Noticed the ground from battery to the frame is getting hot. Is this normal? (possible short somewhere?)

 

[TwoManyXS1Bs]

That ground getting hot could be it. A bad connection, internal to the cable, at a lug crimp, or bolted to frame/engine. Heat is a sign of resistance, too hot and the connection could open up like turning off the ignition switch...

 

[ANLAF]

m00shu

I've been checking out electronics (trying to learn a little) and by coincidence I came across exactly what TwoMany is saying. Sometimes POs fit O-ring connectors that are not compatable with the gauge or amp rating of the wire they are using - result heat. Sometimes the wire becomes broken or separated from the lug or O-ring - usually that means a break or an intermittent break in the circuit. Yes, the heat might well be the starting point for the detective work.

To know whether your charging system is stock remove the lefthand engine Yamaha cover (circular piece held by two 4mm allen bolts) and have a look inside. A stock system is a rotor and stator (there are many pics you can call up to see). Also it will have wires from the r/s to the regulator rectifier. If it's stock there will be five wires coming out of there - four going to the regulator-rectifier and one to the safety relay. I haven't got a safety relay on my bike and don't know where the relay was located on the original. The stock set-up also uses points, but they can be upgraded to electronic ignition such as the popular Pamco and the Boyer units (and still use the stock rotor/stator.

ANLAF

 

[m00shu]

Thanks everyone for your help! Given the latest developments I think I'm going to basically start from scratch. Remove all the wiring and ensure it's all up to par. Tired of tinkering around with no success here.

Again, thank you everyone for your suggestions! I'll update the thread when I figure out whatever is the culprit.

 

[m00shu]

Ok, so it's been over 2 months and still no dice.

Replace starter coil, ignition coil & wires, new halogen headlight, removed reserve lighting box (jumped wires), completely tore down all electrical wires and re-wired everything back together testing with required parts and pieces. Still have the same issue!

So along the way I think I *might* have found the culprit. But have no idea of where to go from here.

How I can reproduce it now:
Removed safety relay
Jump RY w/ BL/B
Start bike rev up just a little over idle (1500ish rpm)
Bike dies

If I remove the jump from RY to BL/B the bike does *not* die. What components should I check from here?

 

[angus67]

m00shu

I've been checking out electronics (trying to learn a little) and by coincidence I came across exactly what TwoMany is saying. Sometimes POs fit O-ring connectors that are not compatable with the gauge or amp rating of the wire they are using - result heat. Sometimes the wire becomes broken or separated from the lug or O-ring - usually that means a break or an intermittent break in the circuit. Yes, the heat might well be the starting point for the detective work.

To know whether your charging system is stock remove the lefthand engine Yamaha cover (circular piece held by two 4mm allen bolts) and have a look inside. A stock system is a rotor and stator (there are many pics you can call up to see). Also it will have wires from the r/s to the regulator rectifier. If it's stock there will be five wires coming out of there - four going to the regulator-rectifier and one to the safety relay. I haven't got a safety relay on my bike and don't know where the relay was located on the original. The stock set-up also uses points, but they can be upgraded to electronic ignition such as the popular Pamco and the Boyer units (and still use the stock rotor/stator.

ANLAF

its a 1981. he has tci

 

[peanut]

I was going to suggest the safety relay but I see that you have removed the connector and bypassed it so it can't be that.

The hot ground wire should be a clue methinks. I suspect that you have a short somewhere.

I would be tempted to disconnect every electrical connector that is not essential to the ignition circuit ie head lights,tail light ,signals,flasher relay alternator and rectifier. see if the fault persists or not. Then its a question of reinstating until the problem reoccurs.

You could also put a ampmeter on the battery to see what the battery and charging system is doing when the bike cuts out.

 

[TwoManyXS1Bs]

...The hot ground wire should be a clue methinks...

Aye, matey! Should be quite easy to temporarily jumper 1 or 2 additional grounds. From battery negative to engine (just clip onto a fin or such), and from battery negative to a clean ground on the frame. If the temporary jumper heats up, then the original ground has a poor connection. If the problem disappears, then the original ground has a poor connection...

 

[peanut]

ok I looked through some electrical schematics as I am not familiar with 1980+ models .

As far as I can make out the connector you have removed is from the Lighting/safety Relay. First an explanation how it works. Please someone correct me if I make an error
The relay contains two switches which operate simultaneously.

One switch disconnects the supply to the headlight when using the starter motor.(RY & LB wires)

The other switch connects and disconnects the starter motor circuit preventing the starter engaging whilst the motor is running.(RW &RW wires)


The black wire grounds the lighting relay coil
The Yellow wire from your Alternator supplies the other side of the coil which energises your lighting/safety relay.

When a current isn't flowing on the yellow wire your lighting relay switches join the two red/white wires that supply power to your starter solenoid switch and cut the RW & LB wires so that full power of the battery goes to your starter motor.

Once the motor starts the current from the alternator (yellow wire ) energises the safety/lighting relay reversing the switches so that the starter solenoid is disconnected and then lighting circuit to the headlight is reconnected.

Ok so if you want to bypass your relay you need to link the two Red White wires together for power to the starter motor and coil etc for starting and running.

Naturally with the yellow and black wires disconnected you will be able to start the starter motor whilst the engine is turning so you need to watch for that.

Link the Red yellow wire with the Blue wire if you want the headlight circuit to work. but I suspect that that is the circuit where your fault lies either there or with your alternator wiring. It would pay to check the wiring where the loom exits the stator as it is very common for the loom to get cut by the stator or cable clamp and cause a short

 

[m00shu]

The hot ground wire should be a clue methinks. I suspect that you have a short somewhere.

Forgot to mention the hot ground wire is no longer an issue after re-wiring everything and re-cleaning/sanding grounding points. In fact I've checked all ground wires for heat and they all feel ok.

It would pay to check the wiring where the loom exits the stator as it is very common for the loom to get cut by the stator or cable clamp and cause a short

Looks like this is the path I'll head down next. Maybe there is something going on when the charging system kicks in and there's too much voltage coming through with the lights so it just shuts down as a safety measure?

Am I missing any other 'safety' relays or auto reset fuses by chance that could cause weird issues?

 

[m00shu]

While trying to follow this guide: http://xs650temp.proboards.com/thread/3461

Step one checked out ok. But I moved on to step 2 which seemed to exacerbate the issue (or so I thought).

I noticed without the safety relay and lights jumpered on the 'dying' issue happens even with the engine off.

With rectifier grounded:

Without rectifier grounded:

Perhaps a bad battery? The voltage is due to cranking and running while it died. If I charge the battery it will hold it's charge for a few days (few days is all I tested).

 

[peanut]

I noticed without the safety relay and lights jumpered on the 'dying' issue happens even with the engine off.


.

you lost me here

if the engine runs ok with the light link out then the lighting circuit is where you need to start looking I would say

Check your electrical schematic .

You'll see that the blue/black wire you are linking to is the 12v+ supply to the tach and speedo illumination bulbs so remove the headlamp and thoroughly check the wires in the headlamp pod and the bulbs/bulb holders in the tacho and speedo and black ground wires from the bulbs back into the headlight pod connector. Look for chafed wires shorts etc .Try removing the bulbs and testing the engine for cutting out.

next you need to check the Red /yellow wire which feeds to the lighting/safety relay from the 20Amp fuse in the fuse block . So check the Red /Yellow wire and carefully check the fuse box and fuse holders etc.