Modern Vespa

I have been replacing my dull incandescent with LEDs. Nothing surprising there except on one side only, the right, I have that rapid flashing which I would have expected without resistors but the left side is blinking normally. Can anyone explain why there is a difference? Peecyooleeahr.

One LED turn signal blinking faster than the other LED turn signal could be due to a difference in resistance between the two circuits. LED turn signals require a certain amount of electrical resistance to operate correctly. If the resistance is too low, the LED will blink faster.
If one LED turn signal has a lower resistance than the other, it will blink faster. It is possible that the wiring or connections for one of the turn signals is faulty, or if there is a difference in the type or quality of the LED bulb used.
Another possible reason for one LED turn signal blinking faster than the other could be a problem with the turn signal relay unit itself.
You can eliminate the LED is bad by switching the two and see if the fast blinking switches sides. Then you will know that it is a bad LED, if not then test the turn signal relay to see if that has gone bad.

FTFY... The resistors used with LEDs are connected in parallel, to reduce the resistance as LEDs have a much higher resistance than incandescent bulbs.

It's the same effect as if a bulb blows, the resistance of the circuit doubles and the flasher goes faster to warn you.

I reversed my words, thank you for correcting me.