Bert was commenting about how crude these air cooled engines are along the lines of oil filters don't matter much. I wonder. An old flathead sure but these newer OHV? Hondas and Kawasakis are crude?
The last Yamaha motorcycle engine I pulled down had metering jets on every cam bushing on the DOHC head to control the oil flow
Every where else the oil hole drillings were different sizes to get the right oil pressure / flow to do the job required
It was 500 cc , produced 6 times the torque of their 500cc mower engine
Mower engines have 2 at best oil holes ( if any at all ) and use splash to lube everything other than the big end and even then some still use splash for that.
Have a good look at the rockers , nearly all of them are simple spring loaded ball & sockets not full shafts & bushes .
So yes rude rude & unsofisticated
Which by the way is what you want for a lawn mower that will be used , abused & neglected
Do not conflate crude with frail or unfit for purpose.
The prime criteria for a mower engine is to be cheaper than the opposition in every Hp rating .
So oil filters are quite arbitory & argueing about them dose little than display the lack of understanding about engines & lubrication .
The addition of external oil filters is more of a sales gimmick than a requirement for the particular engine over it's designed service life.
For decades both B & S and Tecumseh had an oil filter fitted that just circulated oil from the sump through the filter then back to the sump .
Even now when you read specifications you will see "External oil Filter " on one engine and the next one up in price will be labeled "Spin on oil filter with pressure fed crank shaft " and on a few "Spin on oil filter with full pressure lubrication "
All 3 are different , first is just splash , second has oil to the big end only , last has oil to big end & upper crankshaft bush .
Not a single one I have pulled down have rolling element support of any type for the crankshaft , or even a thrust race to support the crank
