For info: I emailed classiccarleds who replied as follows:
The flickering with the LEDs can be caused by a number of things, RF from the coil being primary however, we'd recommend checking:
The earths and live contacts at the lamp holders and also the flasher relay. LEDs need better contacts than incandescent lamps will suffer. Vibration from the bike when the engine is running may be causing loss of contact which LEDs will show immediately.
A drop in voltage. Make sure you have 6 volts at the lamp holders when the bike is running.
Your indicator switch. Make sure the switch is in good condition and the contacts are clean.
Using a multimeter, ensure there is no ripple (AC) in the electrical supply.
