Hi, I have an 08 timecutter Z5060. I bought it in August of last year when I came home from a deployment to Kuwait. It worked great last year. I was able to have a great cut at top forward speed. After having mowed my lawn (about 1.3 acre) 3 times this year it now has two strips of uncut grass between the three blades. I have sharpened the blades, when that didn't work I replaced them (with the OEM Toro blades). Still no luck. When I cut at a slow walking speed it still cuts great. I only mow with full throttle and have done 3 oil and 1 spark plug change. Any suggestions? How do you adjust the belt that goes to the mower deck and how do you know how tight it is supposed to be. The only other thing I could think of is if the belt stretched? Great motor and great mower till now. Thanks for your help. I called the Toro trouble shooting but they just tell you to bring it to a dealer..