XS11 Off Idle Stumble

[cajun31]

Bonz, the bike is running great. It was a weak Dyna coil.

Any ideas on what caused the coil to weaken?

[DEEBS11]

Cajun31, I measured the primaries and secondaries of each coil with a meter. The old failed coil and the new, out of the box coil and the numbers are identical. The issue with the coil is nothing you can measure when it is out of circuit. However, put a load on it and the bad coil is weak enough to cause erratic motor stumble at lower RPMs. Must be an internal short between windings (probably secondary). The coil works but is not correct due to decreased windings caused by an internal short. Perhaps by just a few windings.

[cajun31]

I see how thoroughly you check every thing and was the reason I asked. I can't remember anyone reporting a failed Dyna coil, of course I could have missed it. From what I have read it seems that heat and electrical overloads are the main culprits in causing coil failures. Vibration is another factor.