based on the paint covering the bolts and the valve-cover gasket it had never been done before in the life of the tractor. Of course, it is the product of 1990's Japanese Industry, so it was dead on on every valve and required no adjustment :P
I stupidly forgot to take pics, because I was worried about impending rain, and finishing before said... which amounted to about sixteen drops :P
In any case (stock photos used) it’s a bitch and a half to get to, have to remove the air cleaner, intake runner, and the brackets for the power-steering reservoir, coolant overflow tank and coolant temperature sensor plug...
in order to undo three acorn nuts and pull the cover off.
The fact that there are literally no photos of this engine in any state of disassembly on the net that’s NOT related to a clutch replacement should have a been a clue that I needn’t have wasted my time.
At least you only need one size wrench: 12mm.