Yamaha YBR 125 Custom (Starting problems)

[Englewood]

Hello, I Hope you can help.

I have a problem with my yamaha 125, the bike is struggling to start.

When the bike does start the revs drop and the bikes cuts out, i thought it might off been a bad battery so bought a new one but same thing happend.

The volatge across the battery is 12.4V engine off. When the engine is idle the volatge is around the same, i assumed i should be getting around 14V when the engine is running from the alternator?.

When i rev the bike to 5000 revs the battery volatge stays around 12.5 -13v

Ive checked the voltage on the alternators poles, they are all different from each other reading 80v to 6v AC. (need to check again)

The bike will keep running but struggles to start still, had to push it home the other day .

Could my alternator be dead?.
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Dayonta 675
Yamaha R6
SRAD 600.

[Easy-X]

[Englewood]

Ill check it Sunday. Thanks.
____________________
Dayonta 675
Yamaha R6
SRAD 600.

[jaffa90]

Have you tried jump leads?
Are the battery / leads connected to the bike?
The 3 a/c phase readings should be approx the same.
You could try 3 resistance readings.

[Englewood]

No dont need to use jump leads as when have a full battery the bike starts 1st time but after riding the bike it struggles to start from the electric start but i can get it to start from the kick start.

Its a new battery, im going to check the Alternator readings tomorrow.
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Dayonta 675
Yamaha R6
SRAD 600.

[Easy-X]

Looking at a typical YBR 125 wiring the "magneto" has two wires going off to the "regulator" which then goes off to the rest of the bike electrics.

Disconnect the regulator and check the voltage coming off the magneto. Are you getting a nice range of AC voltage as you rev the engine?

At this point it would be nice to just connect the magneto side to the regulator and see what DC is being produced by the latter (if any) in isolation.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[ThatDippyTwat]

It screams reg/rec - they do go on these. I had to replace one on a 5yr old bike. No idea what the OEM part number is, but I replaced it with a SH640D-12, and crimped (properly) standard Lucar spades on. It's been bomber ever since, still doing CBT duty at the local training school I sold the bike to.
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'98 VFR800 (touring) - '12 VFR800 Crosrunner (Commuting) - '01 KDX220 (Big Green Antisocial Machine)

[Nobby the Bastard]

Reg/rec
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Englewood]

So so ive tested the Rectifier.

Seems ok to me - used diode test on the multimeter.

Negative lead to Neg then positive to diode = 0L on each.
Positive lead to Neg the negative lead to diode = 0.5V on each.

checked resistance on 3 phases of stator all 0.7 OHMS.

??
____________________
Dayonta 675
Yamaha R6
SRAD 600.

[Nobby the Bastard]

If the voltage across the battery doesn't change when you start the bike, the charging circuit isn't working.

If you've tested the compenents qnd they seem fine check the wiring.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Englewood]

Thanks Nobby.

The fuel pump doesnt seem to kick in when i turn the ignition on, the zzzzz sound isnt there anymore.
12.8V acorss the battery.

Fuses are ok, just 2 :-O.

Wiring check next.


Ok, so the bike finally started somehow, ive checked the voltages on the output of the stator (Alternator) and they are all different, 24V/ 16V/ 6V (AC).

When bike is running battery stays at 12.2V, rev bike for a 1 min at 5k revs battery voltage stays the same, i should have 14v from the alternator acorss the battery but i dont!.

So i presume my stator is dead.!
____________________
Dayonta 675
Yamaha R6
SRAD 600.

[Nobby the Bastard]

Disconnect the rectifier and measure the voltage on the non stator side. There should be two sets of plugs, one with three wires and one with two.

You need to unplug the two wire one and measure across that and leave the three wire one alone).
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Englewood]

What voltage should i get across the 2 wires? AC or DC?.

Do you mean the other 2 wires that are connected to the battery from the rec? 11.8 V across them.

Sorry im not sure what you mean, i have 290 ohms across the two wires in the attachment no volatge was reading.

From the 3 wires you told me to forget, if the REC is connected i get 11.8V/13.7V and 4.5V.
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Dayonta 675
Yamaha R6
SRAD 600.

[WD Forte]

I see you tested the resistance between the three white phase wires from the stator (at 0.7 ohms)
but no mention of the resistance from these wires to ground.
This should be in the megaohms region or off the scale on every wire.

If they've shorted to ground you could easily still get the same 0.7 ohm reading between any pair but no output.

Voltage readings are of limited use in that you'll still get some open circuit AC voltage from the windings when spinning the engine over but when in circuit, bugger all current.
(if they've shorted to ground)

Do a proper resistance test first
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bikers smell of wee

[Englewood]

[Englewood]

The fuel pump doesnt kick in beacuse the battery voltage was too low.

The bike starts fine with a fully charged NEW battery but the battery drops when the bike is idle.

The voltage does increase across the battery when reving the bike to 5k but slowly and only to 13v.

When i first bought the bike when the bike was idle the voltage across the battery was 14v. idle

The rectifer diodes are fine - triple checked this.

The AC outputs from the rotor dont seem correct, as ive seen a few videos showing they should be all within the same range of voltage.
____________________
Dayonta 675
Yamaha R6
SRAD 600.

[Easy-X]

Just to be clear: with the rectifier/regulator NOT connected to the battery what voltage are you getting on the AC side and what voltage on the DC side a) while idling and b) with some revs?
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[WD Forte]

[Englewood]

[WD Forte]

[Nobby the Bastard]

[jaffa90]

"""Reg/rec"""

"""If the voltage across the battery doesn't change when you start the bike, the charging circuit isn't working."""

""""If you've tested the compenents qnd they seem fine check the wiring"""".

""""Yep, the three coils should be much the same resistance. The fact that they aren't indicates internal shorts."""

WHAT NEXT NODDY?????

[Nobby the Bastard]

[Englewood]

Well i got a second hand Stator off Flea Bay and we are back up and running.

Thanks guys, till next time .
____________________
Dayonta 675
Yamaha R6
SRAD 600.