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ybr125 starter not firing, batt fine

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Hi all,

My YBR 125 starts fine if I bump it. It then runs fine.

There is plenty of juice in the battery (was at 12.5, but tried trickling it up to 13.3 over night just to be sure, but was to no avail).

When I press the starter button NOTHING happens: no dimming of headlight, no volts getting to the positive connector on the side of the starter, no audible click from any relays.

I tried kicking the side and centre stands up and down lots and worked it up and down the gears lots (as I say it runs fine if I bump start it), did this to try to rule out any switches from the stands or gearbox being broken which might stop the motor.

So I'm guessing it'll be a simple electrical issue, i.e. dead fuse or relay. It is odd that it managed to develop this issue while sitting still for 3 months. I'd have assumed battery, but as I say above it has plenty of volts across it and I've also tried swapping the battery for both the one on my big bike and tried hooking up a car battery in parallel, neither helped.

Does anyone know where the fuse in question is, or relay? I'm trying to find manual now to see if there is a wiring diagram of location of fuse box / schematic of said fusebox, trouble is, I'm not at all good at finding things!!

Thanks for any help anyone can offer.

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Hi, no, no clicks.

Have read the wiring diagram and if I understand it correctly, the kill switch holds one side of the high if its happy. Although its not clear exactly how high, I have had the relay out and both solonoid and switch sides are happy, and it turns out that a full 12v is necessary, so the various combinations of 0.08v, 0.65v & 3.5v aren't going to be enough!

I also just tried fully removing the bikes battery just to check that running it in parallel with a car batt wasn't a fair test, and even with bike batt out and car batt in, it still doesn't work.

So in summary:

1) Battery fine (holds charge, can turn the starter if shorted across it and symptoms present when swapped for a known-good car bat)
2) Relay fine (had it out and on a bench and with 12v across the solenoid, the resistance of the switched side goes to zero)
3) Voltage applied to solenoid when starter button pushed and various combinations of neutral/not-neutral, kickstand up/down & clutch in/out vary. All switches have some kind of effect although they are rather baffling, but considering that their effect isn't trivial and is achieved with simple, read elegant, read cunning, electronics I'm not shocked that they don't simply result in it being zero or 12, but none the less, it never gets to twelve.

So the issue must be with one of the switches which can stop the starter right?

1) I had concluded that the kicker was working cos when I had it running (it bump starts just fine, amazingly well in fact, just takes abotu 5mph and cluch released gently in second and it burbles happily into life!) I accidently cut off the engine by putting the kick stand down.

2) I think the start button is okay cos it does have SOME effect when pressed to the various voltages.
3) The gear indicator certainly shows N on the dash and so surely that is working.
4) Does that just leave the clutch switch? But the thing is, that also shows some effect when pulled to the voltages on the solenoid - they go from 0.04v to 0.08 !!

Confusion reigns tonight.

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  • 1 month later...

I suppose no electrically minded people on this forum then?

I've tried chasing the cables through the bike, the two low-voltage ones from the solenoid that is, and they never appear after disappearing into a conduit under the tank. I know they must end up connected by various means to the neutral, clutch & kickstand kill switches plus the starter button, ground and live, but can't see where they come out.

I have taken apart the kickstand switch and its fine, the neutral & clutch switches I haven't tackled yet. Starter button seems to be in a box which I have to unplug the front break reservoir to get at and that looks scary as the bike works at the moment give or take the need to push start it, and don't want to stop myself being able to ride it to a garage.

I suppose everyone on this forum probably have big yamahas and or would have given up and taken the thing to a garage before trying to tackle dodgy electronics.

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Being rude is no way to get help,not every post get's read.

But anyway remove the small wire at solenoide hook up a volt meter and when the start button is pressed do you have 12 v comming from the start button? Although your scared to remove the start button housing you need to find out if you have 12 v feed to button an if pressed is ther 12v comming out.

If you run a jump wire from the battery + and touch it to the small + wire entering the solenoide will it turn over? If not the solenoide is PMF or if a 2 wire the ground is bad.

Next time just re ask the ? This place has lots of smart peeps just don't piss them off and expect help.

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I had a similar problem with my bike not last week.

Turns out the kill switch was kaput.

You need a decent wiring diagram to do some proper tests.

I ended up pulling the kill switch apart and shorting out the contacts using a screwdriver. Bike fired up fine so for now soldered the two cables together and just using the key.

The kill switch is probably the last component in the circuit before your start button so if your start button has 12v present then start looking at the starter solenoid.

When I checked my switches with a meter they all tested fine, that's checking both resistance and voltage. So it may just be worth linking out one at a time to see which is faulty.

Intermittent electrical faults are a bitch!

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