Hi Mieschi ,
The Clunk is a low noise, it is only apparent at slow speed and is there whether the bike is in gear or not. I think it is coming from the direct drive and sound like it is from the rear wheel area. It would be great if you have an idea as I am perplexed at the moment. It does appear to be only at slow speed under 10klm's but maybe I just dont hear it when I am cruising.