I have an asplund-type whisper chipper that is having issues getting clogged. I have just acquired the chipper (I don't really even know what model it is - need to find that out) and the motor runs well, it powers up good, and at first it seemed to be chipping fine - would yank a 3-4 inch branch right out of your hand and spit it out the other side. But after a few branches it started clogging. It would get a pile of chips just before where the blower air enters the chute. You could still put in a branch but nothing would come out the chute and eventually it would just start collecting a pile of debris in front of the drum. The first time it happened the branch had some vines on it and I thought that might be the issue, but it did it twice more with a simple oak branch only about 2" diameter. The blower seems to be blowing strong. I have not done any maintenance on the drum and I'm now wondering if this is happening due to dull knives??? Any help would be appreciated.