Just about to post, when I realised how long ago this topic was topical! If you had no luck getting the LED indicators to flash reliably & the correct ballast resister is fitted to activate the older flasher units (newer electronic ones don’t need ballast I believe), it’s almost certainly an earth problem on the headlight circuit or with the master switch. Even the slightest earth leak will allow the LEDs to light up, whereas incandescent bulbs need a much bigger voltage drop to visibly glow. I rewired my TS 250 & briefly had an earth fault in the LH switch housing which randomly blew the main fuse. This somehow caused current to find a new route to earth & all the LED indicators turn light up & not flash till the fuse was changed & the short isolated. V odd.