Remove the gear assembly by removing the three Torx screws holding it to the main body, remove gas tank from assembly and set aside without removing gas lines. Remove cover, with blade still installed, that gains access to the gears, remove the large gear and wash out the grease with gasoline. Put penetrating oil like PB Blaster or Liquid Wrench on the end of the bolt at the bottom of the bowel-shaped clutch bell and let it work in. Then, take an Allen wrench that fits the bolt in the small gear and clamp it in a vise with the short end pointing straight up. Set the recess of the bolt on the Allen wrench. This will put the bowl-shaped clutch bell that has 4 holes in it up. Take 2 #2 Phillip's screwdrivers and put them in one of the holes directly across from each other so they form an "X" with the right screwdriver closest to you and the left screwdriver behind the right one.. Then, pushing the screwdriver in the right hand and pulling the screwdriver in the left hand will remove the clutch bell in a counter-clockwise motion. Reverse the above when installing a new gear.