Not starting after gassing up

[FoothillRyder]

Originally Posted by DEcosse

Sorry FR, but that's just nonsense - the ECM draws well under 1 A - sensors draw at most only a few mA each and electronic components have negligible change in operational specs based in a fairly typical operating range from -40 to 150 C

Definitely not nonsense, and it has nothing at all to do with how much current any of those components draw. The ECU sits in a rather small 'pocket' behind the engine, and will definitely be hot after the engine has been running a while. The electrical threshold change I'm referring to happens as a result of the change in temperature, not due to current draw. A typical CMOS circuit actually has switching thresholds that vary over a significant voltage range in that -40 to 150 C operating temperature range.

(I worked for 30 years in the semiconductor industry, dealing with just such embedded processors as the ones used in these ECUs)

[DEcosse]

Interesting background - me too, 35 years.

So what temperature do you think the ECM is at, Ron? It is mounted on plastic and only direct heat source is internally generated or indirect off back-side of the motor which itself is at worst only 100C (& with a gas tank and shock in front of it incidentally) - haven't measured but would be surprised if ECM casing even is > 40C - and not much point in having a control system whose control is worse than the temperature of the engine to which it is trying to regulate!

We can agree to disagree on this

[FoothillRyder]

I'm actually more concerned about the power supply rejection factor. Most devices only guarantee performance over a +/- 10% range, and I could see the battery voltage dropping more than that under adverse conditions (during the start cycle, with a weak cell, etc.).

and yes, we can agree to that - especially since it's all speculation. If you've also been involved, then you know that 'in God we trust - all others bring data'.

[drsib]

Finally had some time today to follow-up on comments and advice.
Popped the seat off and measured voltage across battery terminals and got 12.7V, turned on key (and lights) and measured 11.8, started up on 2nd try and got 14.5. (As an aside, I turned symtec grip heaters on high and still measured 14.5. I then turned my Gerbings vest up to high and measured 13.8V). I left it running in the garage (door open!) for 20 mins or so and still measured 14.5. Turned bike off and measured 12.9. Waited 4 mins and measured same. Turned on key and measured 12.2. Started up with gusto first try (of course).

Took it for a ride and stopped for gas. Started up on first try (of course). Rode home, turned her off and took measurements...same voltages.

BUT, when I tried to restart it failed! I popped the seat and got 12.8V. I cranked the bars all the way to the left and it started perfectly. Sounds like a faulty electrical connection up front, right?

[DEcosse]

Appears like broken key-switch cable

[drsib]

Originally Posted by DEcosse

Appears like broken key-switch cable

Something I can try to fix?

[Joe Houle]

check the harness around(and under) the clamp on the right side of the headstock. Common point of failure.