Toro Engine off its Rocker

[Skywatcher]

Greetings All

A customer brought in a fairly new Toro SS-2400 zero turn mower that wouldn't start. When cranking the engine, sounded like the piston was hitting a compression on every revolution instead of every second revolution. I suspected a dropped push rod. Removed the rocker cover to find that exhaust valve rocker had broken, I've seen bent an broken rockers on intake valves due to varnish build-up on valve stem from using stale gasoline, but never a broken exhaust rocker. Has anyone else run into this failure on these engines?

Parts-Tree and the like indicate the rocker arm P/N 120-4301 has been superseded to a rocker arm replacement kit P/N 136-7885 which includes studs, rockers, retainers and locknuts. This indicates to me that the engine manufacturer realized there was a problem with the rockers, hence the updated version. Is this an unspoken admission of guilt by the engine manufacturer? All the best,

Sky


Machine information

Make: Toro
Model: 74720
Type: SS-2400
S/N: 401074664

Engine (made for Toro)
Model: 121-0799
Type: 452 cc
S/N: 17030002896

[RoyM]

They found a problem occurring frequently enough that it was costing too much money so developed an upgrade. Manufacturers do it all the time.