Your problem is voltage bleed between the right and left blinker banks through the indicator lamp on your gauge cluster. Easiest fix is to wire stock blinkers in parallel up front, wrap in foil and tape and hide inside fairings. Why you ask? LED signals offer super low resistance. Your blinker system relies on resistance to function properly. In the absence of the resistance it wants, your blinkers go too fast, there's extra voltage, the gauge cluster indicator lamp is a bridge to another circuit, so it goes over there and lights them up. A more expensive option would to get some load resistors or a special LED blinker unit or maybe both. Wiring in a set of stock incandescent blinkers will supply the circuit with the resistance it needs to function.