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YBR125 not starting


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Hello,

I have a 2007 Yamaha YBR125 that is not starting for some reason that is more likely to be electrical. 

It was starting fine but when I removed headlight front to check some wiring, it stopped starting. Headlight main bulb also stopped working.  I can see that the power to headlight switch was not coming from headlight relay (which apparently stopped working for no obvious reason) but when I  bypass the relay, headlight starts working.

Now, the bike tries to start and there is spark in the plug but it does not start. I can hear fuel pump priming and there is sufficient petrol in the bike. Side stand switch is apparently working as the bike does not attempt to start when the stand is down. Could someone please point out where to start? 

There are more than one wiring diagrams available over the net but I think I have found the one that is relevant to my bike (based on colour scheme).

I recently changed flasher relay but that is working fine.

Thanks in advance.

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  • 4 months later...
On 9/19/2020 at 1:10 PM, Searcher said:

Hello,

I have a 2007 Yamaha YBR125 that is not starting for some reason that is more likely to be electrical. 

It was starting fine but when I removed headlight front to check some wiring, it stopped starting. Headlight main bulb also stopped working.  I can see that the power to headlight switch was not coming from headlight relay (which apparently stopped working for no obvious reason) but when I  bypass the relay, headlight starts working.

Now, the bike tries to start and there is spark in the plug but it does not start. I can hear fuel pump priming and there is sufficient petrol in the bike. Side stand switch is apparently working as the bike does not attempt to start when the stand is down. Could someone please point out where to start? 

There are more than one wiring diagrams available over the net but I think I have found the one that is relevant to my bike (based on colour scheme).

I recently changed flasher relay but that is working fine.

Thanks in advance.

I know it's a bit late on - if your model is anything like the earlier models, the headlight ONLY comes on once the engine has started (controlled by the ECU - even if you stall it then it stays on until key off). It will give you marker lights front/rear and brake lights only whilst the engine hasn't started.

If you have disturbed any wires behind the headlight, check they're all plugged back in, and in the correct spots.

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  • 5 months later...
On 1/23/2021 at 6:24 PM, sparxooo said:

I know it's a bit late on - if your model is anything like the earlier models, the headlight ONLY comes on once the engine has started (controlled by the ECU - even if you stall it then it stays on until key off). It will give you marker lights front/rear and brake lights only whilst the engine hasn't started.

If you have disturbed any wires behind the headlight, check they're all plugged back in, and in the correct spots.

Hi,

After a while I tried working on the bike again. Situation is pretty much same except that fuel pump stopped working and hence no priming sound. I changed fuel pump and it is now priming. Neutral bulb is blown and the headlight relay is also faulty. Therefore the main beam only works if I short the two poles on the white headlight relay. There is spark on the plug and it attempts to start as it should. 

Some times back the ignition barrel was replaced with an after market one (the one in which black/ white and light green pair of wires opens when switch is turned on but I bridged it with a piece of wire and it was has been working fine.  

I am not sure why but when the bike was starting it only used to start with clutch lever pressed and ran fine when leaver was released after starting. This situation is still present and the bike only attempts to start when the clutch lever is pressed.  Likewise, the bike only attempts to start when the side stand is lifted hence I assume kill switch is working fine.

Spark plug is fairly new and the strength of spark seems normal. Battery is showing a little over 13V at its terminal and most all wires where it should show 12+V. All other electrics are working fine.

Any suggestion on where to start?

Thank you. 

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Hi,

Just a little update. I rechecked the neutral light and it appears that light blue wire that is connecting neutral light to neutral switch is not fully grounded. It is showing some 0.5v while brown is showing 12.6v. When I bridge light blue wire (in the headlight shell) to earth neutral bulb comes on but the motorcycle still does not start. 

Also after earthing light blue wire bike tries to start without pressing the clutch lever. 

Any way to bypass neutral switch to test if that is the culprit?

Any other thing I should look for?

Thanks

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  • 4 weeks later...

On my wiring diagram (for a 2005 YBR), the solid blue wire I think you're talking about runs to the neutral switch - it then connects to ground. The wire appears to run to the generator side of the engine, by the front sprocket. Test the switch directly at it's contacts (should ground likely when in neutral), the wire may also be broken at some point between the front and rear of the bike.

 

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