Not a bad motor at all. Clocked near 500 hrs on a mid 04 craftsman Dyt4000 and going up to date... Zero engine problems, minus a coil pack going out around 200 hrs. Zero oil usage, no valve ticks. Oil and filter changed with a name brand syn every 40 hrs on avg. Engine still has full power, and does not leak or smoke. Even still has the original battery! I would buy another in a NYC sec!. Now the tractor on the other hand... that needed tires, brakes, tie rods, sparkplugs, air filters, fuel filters, oil filters, transmission shift keys & a couple gears and fluid, front grill, belts... although reading through the list it does seem like mostly wear and tear items.
EDIT: I see you are talking about the walk behinds!, also have a couple of these! one is a mids 2005 6.5HP, the other a 2013 7.25. The 6.5HP one is perfect. NEVER an issues, first pull start, NO oil usage, no abnormal operation. Changed the oil many times, always used a synthetic. still have factory pulg, and air filter.
The 7.25 was just bought this year, and well. after leaking out 1/2 the oil out on the ground via the intake after the first use, was going to take it back, but i filled up the oil and it never leaked again.. It smokes on every start up. It also just blew a coil pack YESTERDAY!. 3rd time using it. ykes.