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Yamaha xs500 won’t run

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Jay2903
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PostPosted: 21:17 - 04 Nov 2018    Post subject: Yamaha xs500 won’t run Reply with quote

Hey guys
I’m getting some help from the guys on the xs500 forum but I thought I’d get some help here too.

Basically my bike isn’t running. It sometimes starts on the right cylinder and switching around or replacing the plugs will partially or completely fix it for a short while but then one side will stop firing and it cuts out.

I’m certain it’s an electrical problem the carbs were tuned by a local mechanic who also set the timing.

I’ve replaced the battery (fully charged), condenser, points, ignition coils, plug caps and changed out the plugs countless times.

I really don’t know what else to do
Any help greatly appreciated
Cheers
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jjdugen
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PostPosted: 21:57 - 04 Nov 2018    Post subject: Reply with quote

There is a reason for them being unloved, they basically do this!
From my limited experience, it is usually carb related, double check settings, jets, inlet rubbers, sacrifice a virgin, dance around naked in the full moon, etc.
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jaffa90
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PostPosted: 23:12 - 04 Nov 2018    Post subject: Reply with quote

Have you tried EASY START spray after removing the air filter?
Are the spark plugs wet / smell fuel after trying to start it and have you a cracking blue spark?
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Jay2903
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PostPosted: 03:38 - 05 Nov 2018    Post subject: Reply with quote

jjdugen wrote:
There is a reason for them being unloved, they basically do this!
From my limited experience, it is usually carb related, double check settings, jets, inlet rubbers, sacrifice a virgin, dance around naked in the full moon, etc.


I’ve checked the carbs, the disappearing spark seems to be the problem. When it’s working all the virgin sacrificing seems almost worth it. It’s a fun bike.
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Jay2903
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PostPosted: 03:39 - 05 Nov 2018    Post subject: Reply with quote

jaffa90 wrote:
Have you tried EASY START spray after removing the air filter?
Are the spark plugs wet / smell fuel after trying to start it and have you a cracking blue spark?


Yea plugs are wet.
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jaffa90
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PostPosted: 10:32 - 05 Nov 2018    Post subject: Reply with quote

What supply voltage have you got to the coils?
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bikenut
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PostPosted: 10:53 - 05 Nov 2018    Post subject: jay Reply with quote

Hi jay, you had a kawasaki problem some time ago and hopefully your shed is the bees knees ?!

Loss of spark proved via red neon plug caps ??

You have a wiring diagram for this bike, 2 sets of points or just one ?

Do any of the lights/electricals ( neutral light being favourite ) etc. misbehave when the steering is turned lock to lock???

How are the new points now, quite badly pitted and very white and lots of sparks when the engine is running ?
you said you have renewed points, condesnsers, coils and plug caps.......

Prove loss of ht, then move on to fuel, you sure you have loss of ht ?????

and under what condition, ei cold, hot ?

what year xs and a link to cmsnl would be good......
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Jay2903
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PostPosted: 23:47 - 05 Nov 2018    Post subject: Reply with quote

jaffa90 wrote:
What supply voltage have you got to the coils?


I’ll check that next
Cheers
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Jay2903
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PostPosted: 00:02 - 06 Nov 2018    Post subject: Re: jay Reply with quote

bikenut wrote:
Hi jay, you had a kawasaki problem some time ago and hopefully your shed is the bees knees ?!

Loss of spark proved via red neon plug caps ??

You have a wiring diagram for this bike, 2 sets of points or just one ?

Do any of the lights/electricals ( neutral light being favourite ) etc. misbehave when the steering is turned lock to lock???

How are the new points now, quite badly pitted and very white and lots of sparks when the engine is running ?
you said you have renewed points, condesnsers, coils and plug caps.......

.
Prove loss of ht, then move on to fuel, you sure you have loss of ht ?????

and under what condition, ei cold, hot ?

what year xs and a link to cmsnl would be good......


Hey mate, nice to hear from you. The workshop is working out lovely.

I’m checking spark with the plugs resting on the top of the engine.
There’s two set of points
Wiring diagram - https://farm9.staticflickr.com/8026/7124306475_b2b97269ce_b.jpg
None of the electricals misbehave when I turn the bars
Points look as new, I had the points cover off one of the times I ran it. No sparks or anything unusual.
It’s a 1975
https://www.cmsnl.com/yamaha-xs500-1976-1h2-europe-1h228-198e5_model37275/partslist/#.W-DLlBanyEc
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bikenut
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PostPosted: 11:03 - 06 Nov 2018    Post subject: shed Reply with quote

Its nice doing stuff in a big enough shed, dry and out of the wind, a radio, even a piss pot, kettle and joy of joys some heating !! Luxury.

To the bike, how does it behave with the points cover off all the time, had that many many many years ago, screw down points cover and problems, undo cover a bit and problems disappear. Even one time bike all ok when on stand, then rider sits on bike and no power....yeh you guessed it a rag under the seat blocking the air intake......it happens dudes !

Prove a loss of ht ( even an lt problem hence ht loss ) using the relatively cheap red neon plug caps, they are a good quick visual indicator of ht and ht strength, you cna use them on a road test even, much easier than trying to see a dmm with the leads dangling in the wind, besides htf do you see a dmm screen at night?? going up hill???

Dmm's even analoque meters are great and have there uses, so check lt when the bike is playing up also. Earths are all good, has the frame/engine been painted ???

Rule in or rule out ignition first else round and round the mulberry bush till you fall over, sort, then move onto fuel, tank all clean and the vent good as well as the vac fuel tap??

Valve clearances all good as is compression, no compression loss with heat ?
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Jay2903
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PostPosted: 11:59 - 06 Nov 2018    Post subject: Reply with quote

jaffa90 wrote:
What supply voltage have you got to the coils?


8v both
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Jay2903
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PostPosted: 12:02 - 06 Nov 2018    Post subject: Re: shed Reply with quote

bikenut wrote:
Its nice doing stuff in a big enough shed, dry and out of the wind, a radio, even a piss pot, kettle and joy of joys some heating !! Luxury.

To the bike, how does it behave with the points cover off all the time, had that many many many years ago, screw down points cover and problems, undo cover a bit and problems disappear. Even one time bike all ok when on stand, then rider sits on bike and no power....yeh you guessed it a rag under the seat blocking the air intake......it happens dudes !

Prove a loss of ht ( even an lt problem hence ht loss ) using the relatively cheap red neon plug caps, they are a good quick visual indicator of ht and ht strength, you cna use them on a road test even, much easier than trying to see a dmm with the leads dangling in the wind, besides htf do you see a dmm screen at night?? going up hill???

Dmm's even analoque meters are great and have there uses, so check lt when the bike is playing up also. Earths are all good, has the frame/engine been painted ???

Rule in or rule out ignition first else round and round the mulberry bush till you fall over, sort, then move onto fuel, tank all clean and the vent good as well as the vac fuel tap??

Valve clearances all good as is compression, no compression loss with heat ?


I was playing with it today. The spark is intermittent on the left side but I don’t know what’s causing it
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bikenut
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PostPosted: 12:09 - 06 Nov 2018    Post subject: Reply with quote

8 volts to the coils would seem a bit low, how is ign switch, use wiring diagram, the correct one, and start from the battery working your way methodically to the coils and then the points.

Remember the handle bar test as the wiring flexes, and cam become a make and break or weak contact.....usually showing with a flashing neutral light.....

be methodical and use the wiring diagram, its a street map from a to b.....

new battery so above 13volts when connected to the bike and bike is off, coming down to 12 and a half ish when bike turned on........remember about the handle bar kill switch see diagram to see how that is wired.....
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bikenut
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PostPosted: 11:48 - 08 Nov 2018    Post subject: xs500 Reply with quote

Hi jay, how you getting on?

I don't have an xs500 manual or wiring diagram, but if the 250/360/400 one is anything to go by then the ign system is fused and has a common supply to the coils, seperating into the 2 ign systems after this.

You could just rig up a hot wire direct to the coils suitably switched and fused and run engine on that but the charging system must be plumed in and should be checked it works ok as soon as the engine is running.

There are lots of possibilities for a bad connection and the coils should experience battery voltage.

See the wiring diagram for wire colours as they are different from honda ( green is honda earth, black is honda 12volt after the main switch, so be warned ) and no doubt kawasaki as well.
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Jay2903
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PostPosted: 09:02 - 09 Nov 2018    Post subject: Re: xs500 Reply with quote

bikenut wrote:
Hi jay, how you getting on?

I don't have an xs500 manual or wiring diagram, but if the 250/360/400 one is anything to go by then the ign system is fused and has a common supply to the coils, seperating into the 2 ign systems after this.

You could just rig up a hot wire direct to the coils suitably switched and fused and run engine on that but the charging system must be plumed in and should be checked it works ok as soon as the engine is running.

There are lots of possibilities for a bad connection and the coils should experience battery voltage.

See the wiring diagram for wire colours as they are different from honda ( green is honda earth, black is honda 12volt after the main switch, so be warned ) and no doubt kawasaki as well.

Yea I took a look at it yesterday.
1st I checked the spark it appeared to be fine
I put the plugs in and it didn’t start
I pulled them and the right side had no spark
I switched the plugs around and the problem switched sides.
I noticed the right ignition coil was quite hot.
Is there something that could be causing the plugs to stop working ?
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Jay2903
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PostPosted: 09:03 - 09 Nov 2018    Post subject: Reply with quote

I topped up the battery it’s 11.7v at the coils
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jaffa90
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PostPosted: 11:13 - 09 Nov 2018    Post subject: Reply with quote

Jay2903 wrote:
I topped up the battery it’s 11.7v at the coils


What is the battery voltage after being off charge for 12 hours?

A hot coil can be a long time feed of input voltage instead of a blip so what is happening when you kick start the engine using the meter?
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Jay2903
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PostPosted: 13:28 - 09 Nov 2018    Post subject: Reply with quote

jaffa90 wrote:


What is the battery voltage after being off charge for 12 hours?

A hot coil can be a long time feed of input voltage instead of a blip so what is happening when you kick start the engine using the meter?


It was 13.5 I think. It at 13 now.
What do you mean by kickstart using the meter ?
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jaffa90
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PostPosted: 13:55 - 09 Nov 2018    Post subject: Reply with quote

When turning the engine over you should get a input voltage blip at the coils, this is when the points start to open.
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Jay2903
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PostPosted: 15:55 - 09 Nov 2018    Post subject: Reply with quote

jaffa90 wrote:
When turning the engine over you should get a input voltage blip at the coils, this is when the points start to open.


So I’m kicking the bike with one wire of the multi meter connected at the plug cap and the other to a ground.

Both coils peak at around 16
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jaffa90
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PostPosted: 18:15 - 09 Nov 2018    Post subject: Reply with quote

No no no,your not reading the message, i`m talking about the input (low tension voltage) at the coils not the output high tension voltage which is thousands of volts at the plugs.
When the points open (2 of) a pulse of low voltage goes to respected coil and a high voltage comes out and goes to the spark plugs.
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bikenut
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PostPosted: 11:48 - 10 Nov 2018    Post subject: igntion Reply with quote

examine the wiring diagram and "understand" the circuit, its not that complex, then read up on how the cb points type of igntion system works, again thats not that complex, a "transformer" if you will, and a colapsing magnet field.

When the points open, the current flowing thru the 12volt ( low tension, LT ) which has now been switched off, the magnetic field crated by the flowing lt "collapses, with the magnetic lines of force being really attracted top the soft iron laminated "core", as they really love each other !

The collapsing magnetic field "cuts" thru the many many many many many many many many many many more High Tension ( HT, spark ) wires inside the coil. Cut a magnetic field with a wire and a current/voltage (EMF but now we are getting quite technical, do you really need to know about tuned circuits ?? ) is induced into the wire, which can end up as being quite high, HT, a spark. voltage of about 25k volts but little current.

A fouled plug can/will cause a misfire, so both plugs must be clean else tracking ( look for a lightening type burn mark ) will occur. Look inside the plug cap and the plug insulated end that goes into the cylinder. The other end of the plug is stepped but that may have a track mark. Sometimes a lack of light will help you see HT "leakage" just look at the power pylons when its a damp night, you can see and even hear the leak ) .

Gety the inexpensive red neon plug caps I have been banging on about, A relatively cheap ign aid tool, you can see the ht ( or its loss ) and judge its strength, when the engine is cranking and running ( or missfiring ) . You may have to make an adaptor to fit your plugs and plug caps but money and time well spent. They work on cdi systems as well. they can save hours of hair pulling fun, but if that's your thing then just keep having fun until your bald !
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bikenut
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PostPosted: 11:59 - 10 Nov 2018    Post subject: Reply with quote

If I am correct, your xs has 2 individual ign systems, both sharing a common "live feed" from the battery, thru the main ign switch, thru the "kill switch" and then branched to the 2 individual coils and contacts systems.

As said study the wiring diagram so you know the system, and how it works.

Get the red neon plug caps for testing, even by riding the bike at night.

HT coils can pass the resistance check all fine and dandy, band even allow the engine to run on that cylinder, but break down under load and misfiring.

You know the resistance of the coils 2 coils of wire inside ??

And the removable ? ht wires are all ok ?

Check with a fully charged battery the voltage across the battery when cranking and note down.

Check the voltage at the twin coil connector ( disconnected from the coils ) when cranking and note down. Compare, they should be the same, or very very close.

ASs said earlier you can hot wire the coils from the battery but make it fused for safety. This eliminates the bike wiring from the circuit apart form lt from the coils to the points.

Have you been doing any painting of the bike by the way as paint can be a really good insulator.

The red neon plug caps can show you a lot.

If one cylinders plug repeatedly gets fouled ( black carbon deposits causing tracking ) which stays on that cylinder, suspect carb/fuel problems on that cylinder
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Jay2903
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PostPosted: 15:02 - 10 Nov 2018    Post subject: Reply with quote

bikenut wrote:
If I am correct, your xs has 2 individual ign systems, both sharing a common "live feed" from the battery, thru the main ign switch, thru the "kill switch" and then branched to the 2 individual coils and contacts systems.

As said study the wiring diagram so you know the system, and how it works.

Get the red neon plug caps for testing, even by riding the bike at night.

HT coils can pass the resistance check all fine and dandy, band even allow the engine to run on that cylinder, but break down under load and misfiring.

You know the resistance of the coils 2 coils of wire inside ??

And the removable ? ht wires are all ok ?

Check with a fully charged battery the voltage across the battery when cranking and note down.

Check the voltage at the twin coil connector ( disconnected from the coils ) when cranking and note down. Compare, they should be the same, or very very close.

ASs said earlier you can hot wire the coils from the battery but make it fused for safety. This eliminates the bike wiring from the circuit apart form lt from the coils to the points.

Have you been doing any painting of the bike by the way as paint can be a really good insulator.

The red neon plug caps can show you a lot.

If one cylinders plug repeatedly gets fouled ( black carbon deposits causing tracking ) which stays on that cylinder, suspect carb/fuel problems on that cylinder


Alrighty, I’ve checked almost everything but I’m gonna go back over it and make note and get some plug caps.

If I wire the coils from the battery and it still doesn’t work what else could it be ?
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jaffa90
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PostPosted: 18:29 - 10 Nov 2018    Post subject: Reply with quote

"""If I wire the coils from the battery and it still doesn’t work what else could it be ?"""
You will over heat the coils with a constant input voltage. Shocked
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