I purchased Timecutter 4220 with the 21 Kohler about four months ago. Since the first time I used it, I have had problems with clumping. I've tried to eliminate every possible reason this may be occuring: grass is not wet, grass not too high, cut is not too close (I can actually cut the very next day after a cut and still have the clumping issue). I called my Toro dealer and he gave me the stock answer that the grass is too wet and did not have any idea what else it could be. Any help on what I could do to correct the problem would be GREATLY appreciated.