I don't respond to PM's as it defeates the entire reason why this is a public forum.
Vertical shaft engines are made exclusively for mowers.
The mower market is very price sensitive so they are made cheap as possible.
Cheap means more maintanance.
Cheap means cheaper materials, cheaper processing and cheaper designs.
Honda refused to make cheap engines and left the sector, now only making walk behind engines.
Motorcycles are also air cooled as are horizontal shaft engines.
Mowers have a design life of around 10 years.
Joe average spends 2 hours on a ride on around 25 times a year so 2 x 25 x 10 = 500 hours. That is the design life of a domestic ride on engine.
Commercial engines look identical but are not they use substantially better metal and a better design to attain the same 10 year life.
Joe Average lawn care mows around 5 hours a day for the same 25 weeks so.
5 x 5 x 25 x 10 = 6250 hours which is why they are much more expensive.
Horizontal shaft engines work longer hours and are also designed for a 10 year life span but because they are generally used all year round they are good for around 10,000 to 15,000 hours.
Engines are priced accordingly domestic engines are around 2/3 of a commerical which is about 2/3 of a horizontal.
The most expensive item in an engine is the crank,
The cheapest way to form metal is casting ,
The most expensive way to form metal is forging.
Thus domestic engines have cast crank, commercial engine have forged cranks.
This is most obvious with the old Kohler engines where the Courage ( domestic engine ) cast crank is bigger, thicker & heavier than the Command ( Commercial engine ) forged crank which is thinner, lighter & stiffer.
Then there is oil transport.
Most domestic engines have oil feed to the big end and splash for everything else where as a commercial engine will have pressure feed to all 3 crank journals.
Some brands like JD for example try to make a better quality machine so they get vertical shaft engines made with forged cranks and you see them labled as G4 Crankshaft.
