Kohler ch 25 c with very little power

[kartingdad]

Trying to fix a mower for a friend, it is a Simplicity with a 60 inch deck, made somewhere in the 1990's . seams to run ok, but at full throttle it tops out at around 3200 rpm's, and when I throw the deck on it drops to 2700 and that is all she will do, start to move and it drops more (maybe 2200 max). The deck spindles all seam good, new belt on the deck, fuel filter and plugs. The cylinder on the left side has 160 psi compression and the right around 145 psi. Motor has 925 hours. Here is what is on the spec tag Family SKH725u1g2ra, Model number CH 25C, Spec no. 68583 , Displ 725 , serial # 2731610081. Any suggestions on what to check next. Thanks Don