stuttering fzs 600

[Fazerider]

Must admit to being a bit puzzled by this as well.
Regulator rectifiers can fail in two ways: either delivering no electricity to the battery, in which case the sparks would have held up until the battery voltage decreases, but you'd spot all the usual symptoms of a dead battery in that case. Alternatively they can stop regulating, which means the full output of the generator is forced into the battery causing the voltage to rise. (My brother had an Audi with that problem... he liked the extra-bright headlights, but it killed the aftermarket transistorised ignition unit!)
Unless you also had a poor connection to the battery it's hard to see how either condition would cause a stutter, and I'd have thought you'd have also noticed the lights changing in brightness.