Yamaha YBR 125 problem....help!

[palace15]

Hi, 2 miles short of a 70 mile ride I lost all power, I was doing about 50mph on my 2007 FI, on a straight road and suddenly without warning I was coasting to a halt. I have a neutral light working but NO orange engine management light, when I turn then ignition on I do not hear any whirring of the fuel pump, the electric start has not worked for sometime but has always started on the kickstart, I have checked the fuse and battery terminal leads and all are fine, I have not investigated yet but am hoping/clutching at straws an electrical wire/plug has come adrift. Just going to have a little investigation either later tonight or first thing in morning before the RAC are called, oh, still have a quarter tank of fuel, I checked that first!!
Many thanks in anticipation.

[Walkabout]

I know nothing about that bike, but I would have the spark plug out and be looking for a spark with the plug earthed to the engine, and a strong smell of fuel coming through from the spark plug hole.

You don't describe any spluttering/mis-firing before the bike stopped which might point to an "instantaneous" failure of an electronic component in the ignition circuit.

[palace15]

Thanks for your reply, at one point I was merrily going along and the next it was if someone turned off the ignition, no warning ...nothing, NO spark at the plug, I have turned the ignition on and pushed and pulled wires hoping for the fuel pump to burst into life or just hoping to see life in the 'engine management light', not until I get home to where the manual is, that I will be able to find the location of the ECU.

[Walkabout]

Originally Posted by palace15

not until I get home to where the manual is, that I will be able to find the location of the ECU.

There are plenty of links in the WWW about the ybr, such as this one about the wiring diagram:-
YBR125 (2007) wiring diagram and technical (really technical) spec. - Yamaha Streetbikes/Sportsbikes - Yamaha Owners Club
Apparently, the ECU is somewhere under the seat/fuel tank and it has 18 pin connections.

Good luck with the fault finding but it sounds like a case of RAC recovery!

[palace15]

Told by the RAC Telephone operator not to remove my fuel tank or the patrol guy will not look at the bike When he arrived he said its either the ECU or CDI unit with the cdi more likely to be at fault,and pointed to the 'cdi' under the side panel, I got a total recovery home and checked out my workshop manual and the a 'cdi' unit is not shown in the diagram? The cdi that the RAC guy pointed to is in fact The headlight relay!!. I removed the tank and sitting on the top frame tube is the 21pin ECU, when touching the mass of 21 wires and plug, everything works fine, so do I have a broken wire or a bad contact from ECU to plug? Time will tell.

So how much did it cost the RAC to sub contract a total recovery of 70 miles one way journey for the sake of a 10minute job removing(not even completely) the fuel tank?

[Walkabout]

I'm not too surprised by the actions of the RAC; it is nearly 50 years since I called them out to a motorbike breakdown - and that's a long story that is
I agreed with your idea of calling them out because you seemed to be at a distance from home base (as I was).

18 pins or 21: well the website I found was US based so it may deal with a different, "export", model of ybr; after all, all bikes are export models to some market or other.

I would start with the simple possible answer; the plug terminals. It's not as if it is an old bike.

I've recently written in another thread that there would be value in a new thread about modern bike electronics and the diagnostics available; I don't feel that I know enough to start it, but I sure would like to read more!!