Model is R 124TC this years 2017. Is not an endurance model. One big plus over the BS on my current mower is that at least this has an oil filter. Whoever designed an engine without a filter!
I used to think that way myself but having been a service tech for the past few years has really changed my mind.
I see 40 year old side bangers running quite fine with little evidence of excessive wear, provided the owners actually changed the oil.
Considering that most mowers are seasonal and most owners change their oil at the end of the season, not because the oil is worn out but to avoid the problems of the engine sitting there with dirty ACID oil in the engine and no oil filter will pull out acid by products.
If any modification is needed to the oil system, it is an low oil shutdown because low oil damage out numbers dirty oil damage 100:1 on the mowers coming through my gate.
Next the market gets what the market will pay for and the market wants cheap not good and to be honest the average desk pilot mower buyer would be hard put to work out what was and was not a good mower or a good feature of a mower engine.
Mower engines are under very little stress, just think about it.
Your 400 cc engine is putting out a whopping 17 Hp
A motorcycle engine of the same capacity is putting out 70 Hp