OK guys I went back to OEM blades last year. It mowed fine, now to this year we got started and switched to a new set of blades because I could feel a vibration. Changing the blades got rid of the vibration. But now we are back at the clumping problem. The blades look the same but they have different part numbers. I put the old set back on and it still clumps. Every thing is sharp and the deck is clean. To me the blades don't look like a mulching blades.they just have a straight cutting edge. Most of Deers mulching blades have a elevated part of the cutting edge. Can you guys give me a part number.
Also do you guys think that it might be possible that I have lost a few rpm thus causing the clumping issue?