My Toro MX 4250 residential zero turn mower, has 200h of service over 8 years… which is not very much.
Above is a recent capture of battery voltage (red) and battery current (blue) using a Hantek 1008C that was under evaluation. (The image colours were inverted for the article.)
Valve lash measurement
Starter current measurement hinted that valve lash was incorrect in at least one cylinder
The exhaust valves should be 0.15-0.2mm lash, and were measured within that range for one cylinder and between 0.2 and 0.25mm (Cylinder #1). This probably accounts for the difference in cranking current at compression, the compression relief is degraded by excessive valve lash.
The inlet and exhaust valves were adjusted as needed.
Above is a capture of starter current after the valve lash adjustment. Note that the peaks in each pair are approximately equal.
Spark plugs
Spark plugs were removed and inspected. The gap was good, the electrodes had sharp corners, Nevertheless, new plugs were reinstalled (per the service manual).
Leak down test
A leak down test was conducted using an OTC 5609. Leak down was less than 1% @ 400kPa in both cylinders, excellent.
Oil change
Oil and oil filter changed.
Fuel filter
Fuel filter changed.
Air filter
The prefilter was washed and re-oiled. The paper cartridge was pretty clean, but was blown out with compressed air.
Control dampers
The right hand control damper is not effective, and sufficiently bad to impact driving.
Replacements are unavailable at this time.