This usually happens when a light bulb is out.
Look around your motorcycle for a blown bulb.
When a light bulb gets burned the total load is reduced and this causes some light to flash faster than normal.
The back right signal light bulb was blown in my case.I replaced it and everything went back to normal.
If all bulbs are ok then you probably is a grounding problem and you got a bad ground wire somewhere.
This fix can also be applied to cars.