Wish i didnt. got it running and it moves ok on the flat and slight uphill, But on a steep incline it quits moving. looking at the rear the fan on top is spinning fast so i believe the belt is doing its job.
If you got a model like my dad's L120, the hydro is "not good". After the original motor blew, dad found a L100 with a bad rear. The original hydro is fine going forward, but as it got warmer, reverse slowly faded to non-existent. Swapped the rear out of the L120 into the L100 and got another year and a half until the motor grenaded last weekend. Oh... and it's a Kohler Command.
Those have the Tuff Torq K51A. They are notorious for stripping out the drive pulley splines. Check to make sure the pulley is on the shaft tight. If that is ok, check the oil level. Replacement oil is 5w50 synthetic motor oil.
I don't know about the stats of a 500, But I used one at work for 8--10 years and it did a great job and never failed to do its job! 700--800 hours on it when I retired, and it was running and all just as it always did! The 500 series was good mowers 500-530--540 Ones I have seen are anyway!