Having spent hours stripping down and replacing the whole wiring for the indicators on a cbr600 custom bike, trying to sort what I thought was a simple fault. One side flashing fast. It turned out to be the bulbs. They where the correct bulbs and wattage but one was a Chinese replacement off ebay . It looked the same and was stamped the correct wattage but it was out enough to trigger fast flashing on one side. The filament on the chinese one looked a tiny bit thinner so it must be a slightly lower wattage. So just incase this problem is driving you insane, swop all the bulbs round first and see if the fast flashing swops sides.