every 100 hrs. , what does oil on dipstick look like? if black i would change oil & filter soon as well as air filter, fuel filter, spark plugs, clean engine cooling fins after removing blower housing, i use a shop vac on engine, visual inspection of coil, adjust valves with engine cold, inspect blades for sharpening or dressing up with a file, i prefer the file method & balancing blades, inspect all belts, pulleys, & bearings for wear , grease unit, check tire air pressures. I guess that about covers it, let us know how it goes, thanks, Mark
One more thing, keep water hose away from mower, water & electrical components & mechanical parts do not go well together, corrosion, rust, & component failure will occur prematurely, use a leaf blower after each use.