I'm with ya here because I've had the exact same thing happen. I've always used the standard clunk and I found my screen completely plugged with fibers. Same with my nephew's DA50 and he doesn't use the fiber clunk either. I can't say for sure where it's coming from but I'm leaning towards the fuel or else the fiber stuff's in the tank when they are new. After cleaning my carb and putting in a kit with a brand new screen, I haven't had any more troubles and that's been a pretty long while back.