New 46" Cub Cadet (purchased n May). It hasn't cut evenly since day one. I've leveled the deck (it was over 2" off when delivered) adjusted tire pressure (came with double recommended pressure in three tires), and replaced the factory blades with heavier commercial blades (verified right side up). The left side mows flat and even, while the right has always been uneven, and leaving some pieces uncut. I clean the top and bottom of the deck after each use, and have removed the pulley guards to make sure nothing is hiding.
This is what I would try. First, remove the deck and make sure both spindles are turning very freely. If the right side is slightly tight, it will spin slower resulting in difference in cut. Second, swap the blades around and see if it makes a difference. Do this after making sure both blades are sharpened to the same angle and balanced. You may have a bad blade, it does happen. Third, I’m assuming the right side is the discharge side. Make sure that there is nothing to hinder discharge, causing a buildup slowing the blades down. Try raising the discharge chute.
Pay attention to what @Rivets said.
Also, heavier commercial blades are not going to help any. In fact, they may actually give you a worse cut. Your blades need to be OEM or of direct replacement dimensions. The heavier blades are a strain on your parts.
