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Yamaha YS125 starting/cutting out issues

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BRUN
Two Stroke Sniffer



Joined: 10 Oct 2020
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PostPosted: 14:32 - 22 Feb 2021    Post subject: Yamaha YS125 starting/cutting out issues Reply with quote

I have a 2017 YS125 which I bought to practice on, waiting on my Mod1/2 which keep getting cancelled due to lockdowns

I had been riding it without issue for a few months, washed it which id done many times before, applied ACF50 and put it away for winter

Now the weather is better, I tried to get it out a few weeks ago just to make sure it still started, which it didnt, turned over fine but just wouldnt fire up, as I hadnt kept the battery charged over winter i thought id killed it, maybe a dead cell etc, so bought a new one, exactly the same.

I followed a fault finding thing in the manual about trying to start it with side stand, in gear etc etc, basically testing the side stand switch, neutral switch, and clutch lever switch, I followed this numerous times and it seemed to point to the neutral switch, even though ive never had a problem with it indicating which gear im in, or neutral, so I bought one and fitted it, still the same. In fact after I fitted the new switch, and cleared the fault code, it started fine 6 times in a row but then started playing up again.

The bike will bump start, ive had it running a few times since, also changed the oil and filter yesterday too so thats fresh and level spot on.

On Saturday after fitting the new neutral switch I thought it was sorted, so got my gear on and went for a ride, as i put my gloves on to set off, it stalled whilst idling, but started up again ok so off i went, got about 500m+ away from my house and turned back, and along a perfectly straight road towards home, it cut out on me 3 times within the space of 200m, managed to get home and it cut out again, so I put it away for the day as it started raining

On Sunday, after the oil change, I managed to start it and left it idling for a bit, went around our estate to test it out and it stalled whilst doing a tight turn but I think that was me not giving it enough throttle tbh, managed to bump it back at the house and the mrs took it out around the estate a few times and it was ok for her, running out of time I went to put the bike away, and with it still running I turned the handle bars full lock to take the key out with steering lock on, but before I touched the key, it cut out as i turned the bars

Bike has a full tank of fresh fuel and the oil level is perfect

Im wondering if their is a bad connection or broken wire around behind the headlight, that moves when turning, which Im going to have a look at this coming weekend hopefully, but im posting on here for any other suggestions or ideas
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WD Forte
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PostPosted: 15:11 - 22 Feb 2021    Post subject: Reply with quote

What I do with intermittent faults is try to 'force the fault'
by wiggling the cables and connectors to see if it has any effect
You may have to remove some plastics to get access to them all but
if/when you locate the problem and fix it, you get confidence in the bike again.

I'd also open check and clean all connector blocks and spray contact cleaner in them all
Also check the brass terminals are properly latched in the block
and havent receded away from their matching counterparts.
Cables like to break near the crimp if stressed, so check for that too.

Broken cables in the loom are a possibility of course but in my experience happen mostly on
much older high use/mileage bikes.

I've seen and fixed poor solder joints on relatively new bike ignition switches too

Apparently the YS125 is an evolution of the YBR125
The YBR has a rats nest of cables and connectors stuffed behind the headlight and would imagine
the YS to be similar so be prepared to whip it orf and check in there too.
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Last edited by WD Forte on 15:13 - 22 Feb 2021; edited 1 time in total
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Evil Hans
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PostPosted: 15:12 - 22 Feb 2021    Post subject: Reply with quote

I'd pull off and clean all the plastic loom connectors behind the headlight / speedo / ignition switch - maybe give them a shot of contact cleaner.

Edit: WD Forte beat me to it!
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BRUN
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PostPosted: 15:33 - 22 Feb 2021    Post subject: Reply with quote

Cheers, I planned once the headlight was off and I could see things a bit easier, to wiggle all the wires behind there, hopefully its not too much of a rats nest lol, also hopefully i dont find a nest Laughing i work at a car dealers and we have had a few cars in the past with mice/rats nests playing havoc with electrics as they have chewed through all sorts

Does it sound electrical to you ?

When it does run, and before it cuts out, it rides fine, until it doesnt lol
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Robby
Dirty Old Man



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PostPosted: 15:56 - 22 Feb 2021    Post subject: Reply with quote

Inspect the wiring loom where it goes around the headstock for chafing, and the ignition switch wires for anything pinched/chafing.
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jeffyjeff
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PostPosted: 15:57 - 22 Feb 2021    Post subject: Reply with quote

Yes, it sounds electrical. Usually, electrical faults manifest themselves with immediacy (on-off). Fuel problems will generally cause the engine to sputter a little before it stops. Fuel injection muddies the water a little bit, but even so, most fuel injection problems are electrically related. You say it runs good until it stops...sounds electrical.
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jeffyjeff
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PostPosted: 16:34 - 22 Feb 2021    Post subject: Reply with quote

I would start diagnosis with the switch inputs designed to kill the engine; the side stand switch and the engine kill switch. You say you washed the bike immediately before putting it to storage, that could be significant. You may have a water-induced short, or water may have corroded switch contacts resulting in a poor electrical connection. Disconnect the side stand switch and ohm it with the side stand retracted and deployed. Try jumping the connector to bypass the switch temporarily as a diagnostic step.
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BRUN
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PostPosted: 16:59 - 22 Feb 2021    Post subject: Reply with quote

thanks for all the replies

i had already ordered a new side stand switch anyway, in a bit of a rush really and it was cheap enough
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BRUN
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PostPosted: 06:43 - 23 Feb 2021    Post subject: Reply with quote

looked at it briefly last night, both looms which run down either side of the bike looked perfectly fine, nothing worn through, the bits under the ignition barrel/instrument panel also looked fine, nothing obvious

its surprisingly easy to get the headlight off and get to them, this is my first bike so ive no idea how bad things can be but its very easy to work on

light was fading so i couldnt get more involved, but i think im gonna need a wiring diagram to go any further, if i cant find one then ill have to get it into somewhere as it will be a bit beyond me, have to find somewhere that will do pick up
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BRUN
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PostPosted: 10:07 - 23 Feb 2021    Post subject: Reply with quote

Just to add to this, I have a code reader, the fault it comes up with iirc was P1601 : control unit
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Evil Hans
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PostPosted: 10:43 - 23 Feb 2021    Post subject: Reply with quote

BRUN wrote:
Just to add to this, I have a code reader, the fault it comes up with iirc was P1601 : control unit


Think that's the code for a side stand switch fault, amongst other things.
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BRUN
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PostPosted: 10:49 - 23 Feb 2021    Post subject: Reply with quote

Thanks

Would this cause starting issues though when in neutral ?

funnily enough my new side stand switch has just turned up, so I guess ill find out soon Smile
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WD Forte
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PostPosted: 19:26 - 23 Feb 2021    Post subject: Reply with quote

How did you get this code?
YBRs for instance would display
1 long and 9 short flashes of the engine warning light
to indicate side stand faults

OBD scanners unless matched to the actual ECU protocols can be vague
or even misleading
A pukka Yamaha one should be more reliable
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BRUN
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PostPosted: 19:30 - 23 Feb 2021    Post subject: Reply with quote

I have a code reader but yes its a generic one

I have used it to clear the code but it comes back when trying to start it

I would have to check to be sure but I dont think the engine warning light flashes


Last edited by BRUN on 19:42 - 23 Feb 2021; edited 1 time in total
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WD Forte
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PostPosted: 19:41 - 23 Feb 2021    Post subject: Reply with quote

what does the engine warning light do?
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BRUN
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PostPosted: 19:53 - 23 Feb 2021    Post subject: Reply with quote

not fitted the side stand switch yet, too dark after work still and raining today

just been out to the bike though to check the engine light, it doesnt flash its just a solid orange/yellow light

but, the bike started first go lol, let it idle for a bit, operated the side stand a few times nothing happened but didnt expect it to really, switched it off and key out, tried again, started again Smile

im dubious it would do the same tomorrow or the day after but its promising that its nothing major, which i wouldnt expect either, the bike hasnt even done 1000 miles yet, not even 900 actually

oh and i keep a battery maintainer on the new battery so its always fully charged
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WD Forte
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PostPosted: 20:20 - 23 Feb 2021    Post subject: Reply with quote

I only have the YBR EFI for reference as I work on one for a local guy
but the ewl should light briefly at switch on then go out.

According to the YBR manual if the ewl stays on that indicates a minor fault
and if the engine is stopped by the kill switch (NOT the ignition switch)
any error codes should flash out on the ewl to help point to the fault.
in a long (for first digit) short ( for second digit) pattern.
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BRUN
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PostPosted: 20:22 - 23 Feb 2021    Post subject: Reply with quote

to the best of my knowledge, i dont have a kill switch, but this is my very first bike so i might just not have seen it lol
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BRUN
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PostPosted: 20:34 - 23 Feb 2021    Post subject: Reply with quote

See attached image of the dash panel
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Nobby the Bastard
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PostPosted: 21:27 - 23 Feb 2021    Post subject: Reply with quote

BRUN wrote:
to the best of my knowledge, i dont have a kill switch, but this is my very first bike so i might just not have seen it lol


Big red switch by the front brake lever.
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BRUN
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PostPosted: 21:59 - 23 Feb 2021    Post subject: Reply with quote

thanks

so if i get it started, then kill the engine with the kill switch, will it do those flashes that i can count and try and pin point it better ?
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BRUN
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PostPosted: 22:13 - 23 Feb 2021    Post subject: Reply with quote

just had a look at the bike, no kill switch, no mention of one in the manual either
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BRUN
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PostPosted: 18:02 - 24 Feb 2021    Post subject: Reply with quote

Success of sorts, I can repeat the issue

At a certain angle, nearly full lock right, the bike cuts out, so 100% it's a wiring/electrical issue
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bikenut
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PostPosted: 18:39 - 24 Feb 2021    Post subject: T Reply with quote

Good, either wire pulling out a bit, trapped in steering stops, fatigue make and break contact inside wire due to steering making loom flex....probably...

Get exact wiring diagram ( something you should have got days ago ) and your dmm out.

The hunt is on....be methodical...

When everything works, press horn and turn steering side to side, does horn stop ? To be less noisy, try front brake light instead.....yes I know but you know what I mean.

You heard/read About the Volvo V70 issue ?
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BRUN
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PostPosted: 18:47 - 24 Feb 2021    Post subject: Reply with quote

im struggling to find a wiring diagram online for this bike
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