FJRiders.com

Hello all. I was riding some very curvy roads in Switzerland, near where I live. I was leaning a lot, and at one point the engine stopped completely, in the middle of the curve. I pressed the starter, and it fired up immediately. This is the second time it's happened. Could it be the unit under the saddle that cuts out the ignition when the bike is on its side?
Thanks in advance (2018 ES model)

I've never heard of this. Couple of suggestions:

1. Check for an engine codes that may have tripped.

2. Jump the side stand switch abd see if it goes away. With the bike in any gear, that could kill the motor.

Side stand switch seems most likely to me. As a temporary measure, give it a spritz with WD-40 and see if it happens again.

The lean angle sensor will only cut off the ignition if the bike is on virtually on it's side or at a lean angle of 65 degrees or more... requires an ignition key cycle to reset it once the bike is righted. So, likely not it, but one could check it if you have a suitable protractor.

Yes, check the side stand switch is OK, or sidestand spring maybe not holding it up?? Intermittent?

I'm assuming you weren't running low on fuel (to the point of the F-count active).

No, I wasn't low on fuel, and I wasn't leaning more than 65 degrees. Both times, I pressed the starter and the engine fired up, no ignition key reset

If nothing else works, you could try checking the connection to the lean angle sensor, which is below the tool tray beside the the abs block and is attached by two screws. Wiring goes from it toward the nest of wires near the air filter access point. Check the wiring back as far as you can go. Maybe some wiring got damaged during an air filter replacement.

I managed to sort of figure this out by seeing a video of the sensor, but I couldn't copy the site address. Google it.

Did you notice if it was particular to left or right turns? Left would suggest (as others have mentioned) that your side stand is dropping and cutting the engine.

If I remember correctly, they were left turns. I'll check out the sidestand. Thanks.

Since it is an '18, it has OBD..... prior to 2016 we had a DiAGnostics screen and could monitor the sidestand switch as we played with it... in this case, revert to conditions that will not let the bike start.... sidestand down, in gear, kill switch in RUN and clutch pulled... fuel pump should not run with ignition on, until you raise the sidestand.... see if you got an intermittent one or sensitive at the very end of travel (up). You could also unplug it and test with a multimeter... I think connector is under the left side throttle bodies, might be tough to get at (without airbox off).

It could be something else in the ignition circuit, will have to dig into the service manual if it's not the sidestand switch.

Update: It was the battery. My guru advised me to change it, which I did(Yuasa). Then I went for a nice drive in the mountains in Switzerland, near where I live. I reproduced the exact route from the previous trip when the engine cut off, and Halleluyah!!!, no cutting off. Can a bad battery really cause a problem like mine? Anyway, I just thought this might be useful knowledge for anyone with the same problem.

I could understand it happening while underway with a bad battery connection (loses connection when leaned over), but I would expect symptoms other than cutting out during operation if it was truly a bad battery - especially when there was sufficient power to restart. Would have been nice to know what the voltage was - at rest (ignition off), at idle and at maybe 3000+ rpm. Anyway, it appears that you are sorted out for now, until it happens (or doesn't happen) again. Good luck.

If you could have accessed the diagnostics codes, chances are you would have seen a few ghost codes, e.g., lean angle sensor and loss of communication with the ECU, etc...... (those are still stored as history since you didn't clear them). These will show up when the battery is failing and reaches a certain low voltage state. FJR's love a good robust battery. I'm betting your issue is solved. Next farkle, install a voltmeter so you can monitor battery voltage on the fly. Optionally wire it live and install a switch on it so you can see initial battery voltage before you turn anything on....

You can buy a Yamaha 4-pin OBD adapter harness on ebay or AliExpress pretty cheap these days, and get a cheap OBD reader for ~$5 too. Usint the Torque Pro app on your phone, you can view data and error codes, etc....... I will update the thread with the instruction sheet.....
http://www.fjriders.com/forums/viewtopi ... ss#p117821

Bounce wrote: ↑Tue Oct 10, 2023 8:21 am

10.9 Volts !!?
Were you starting or is the battery toast?

Neither. Key-on for the photo. No charging, lights on, etc.

Bounce wrote: ↑Wed Oct 11, 2023 7:24 am Neither. Key-on for the photo. No charging, lights on, etc.

Seems pretty low to me, especially since headlights don't come on until after engine start.

Voltmeter is a really good idea, especially if you run heated gear, auxiliary lights and other electrical farkles. Not so much to warn of a (rare) failed stator or R/R, but to make sure you are not consuming wattage in excess of what the stator is capable of supplying. In addition, "key-on" voltage and voltage while cranking can provide a quick idea of battery health.

Meh. It was right after installation with things on-and-off frequently during installation. Gnawing on a nearly 20-year old photo (used for examples and not as a diagnostically-exact test reading) seems a waste of energy.

Bounce wrote: ↑Thu Oct 12, 2023 10:19 am Gnawing on a nearly 20-year old photo (used for examples and not as a diagnostically-exact test reading) seems a waste of energy.

Maybe that's why the voltage is low

I dunno. I think we should talk about this more...

...after another beer.

My 2014 didn’t cut off even when it was on its’ side, resting on the bag guards and sliders. Kept chugging along. I had to turn it off manually.

Another vote for the sidestand.