Specific Troubleshooting On The Classic Click-won't Start Issue - T100

Slade · Mar 21, 2021

Hey everyone !

Got an '08 T100 Bonneville last summer, in great state with only about 10k kms. She ran fine until late last year when I started having the issue of the motor not firing, just giving a click on startup. Didn't seem to me to be the battery, as everything would light up and she had previously held up sitting outside through 2 months of cold Autumn and started like a charm. My father could bumpstart it with a bit of a push, though I've myself never managed it

After searching around I noticed many people had similar issues, with the source often times being mentioned as the ECU blocking the startup under a certain voltage. With all the wiring seemingly good (with my very limited knowledge) I figured I'd try a new battery and got a Snell UTX 12-BS. She started up immediately and ran like a charm again for 2 whole weeks, before once again clicking on startup and adios.

So this seems to me like a very specific issue, I'm not sure where it'd come from ? It had been admittedly fairly cold these last few days (around 0°C) and the motor actually did get going for a few seconds until I tried releasing the clutch and it all shut down with a click - and now we're back to the same situation I described in my first paragraph. It seems rather unlikely that the new battery is at fault, but changing it did solve the problem (at least for a while). So if it is the ECU that blocks it under a certain voltage it still doesn't make sense that it would happen again so fast right ? So maybe there's an electrical issue in some place ? Or maybe it's the starter or solenoid, but then I don't get why it worked with the new battery ?

I guess a fix for the future would be to get it to charge every time, but I live in a small city flat with no garage so that's kind of a pain. I've also seen a DIY way to bypass the ECU which I could install. Still, I have some specific data now and would like to pinpoint the exact issue, so if any of you have insights on it it'd be greatly appreciated ? I'll also take the new battery to a garage tomorrow to test its voltage, see if it actually did drop. Also last hypothesis is that I took an unfit battery, maybe too cheap or something ?

Thank you for your help

Alatamoc · Mar 22, 2021

Hello.
I'm not familiar with the problem specific to this model but in general
If the battery voltage falls below 11.5 volts most electronic ignitions will not fire up the spark plugs.
If you have an electrical short or an alarm fitted, either can drain the battery over time.
I've owned several bikes in the past which would not fire reliably from cold if they had not been ridden for 3 weeks or so.

Tricky-Dicky · Mar 22, 2021

Yes unfortunately this seems to be a problem on a lot of modern bikes even the older Lucas and Boyer ignitions won't fire under a certain voltage, its more a case of the ignition amplifier just doesn't have enough charge to fire reliably under lower voltages rather than a built-in function of the ECU so nothing that can be changed via mapping software.

Alatamoc · Mar 22, 2021

I have some experience of 865 Bonneville Americas ...basically the same engine.
Sometimes the cdi ignition unit fails or the crank sensor does.
But in either case the bike shouldn't run at all...battery charged or not.
Other than that these are pretty reliable machines.
I'd suspect an electrical drain is causing the problem you describe.

Jalapeenoz · Oct 19, 2021

Slade said: ↑

Hey everyone !

Got an '08 T100 Bonneville last summer, in great state with only about 10k kms. She ran fine until late last year when I started having the issue of the motor not firing, just giving a click on startup. Didn't seem to me to be the battery, as everything would light up and she had previously held up sitting outside through 2 months of cold Autumn and started like a charm. My father could bumpstart it with a bit of a push, though I've myself never managed it

After searching around I noticed many people had similar issues, with the source often times being mentioned as the ECU blocking the startup under a certain voltage. With all the wiring seemingly good (with my very limited knowledge) I figured I'd try a new battery and got a Snell UTX 12-BS. She started up immediately and ran like a charm again for 2 whole weeks, before once again clicking on startup and adios.

So this seems to me like a very specific issue, I'm not sure where it'd come from ? It had been admittedly fairly cold these last few days (around 0°C) and the motor actually did get going for a few seconds until I tried releasing the clutch and it all shut down with a click - and now we're back to the same situation I described in my first paragraph. It seems rather unlikely that the new battery is at fault, but changing it did solve the problem (at least for a while). So if it is the ECU that blocks it under a certain voltage it still doesn't make sense that it would happen again so fast right ? So maybe there's an electrical issue in some place ? Or maybe it's the starter or solenoid, but then I don't get why it worked with the new battery ?

I guess a fix for the future would be to get it to charge every time, but I live in a small city flat with no garage so that's kind of a pain. I've also seen a DIY way to bypass the ECU which I could install. Still, I have some specific data now and would like to pinpoint the exact issue, so if any of you have insights on it it'd be greatly appreciated ? I'll also take the new battery to a garage tomorrow to test its voltage, see if it actually did drop. Also last hypothesis is that I took an unfit battery, maybe too cheap or something ?

Thank you for your help
Click to expand...

I just posted a similar issue with my 2010 T100. Were you ever able to pinpoint the cause? Was it solely just the battery?