Just got bored so heres a list of what I believe to be the ranking order of lawn tractor engines. This covers reliability, power, cost of parts, ease of maintenance, etc. It's just an on-the-spot collective view of them, so don't take it too seriously. It is only a reflection of my own experiences with all types of engines in a company and home shop environment. I'll sort them by number of cylinders and layout. i.e. single, opposed, vtwin. And valvetrain. i.e. flathead, OHV, and OHC. This is only for gasoline powered engines. If you'd make any changes, let the reply war begin!
V - Twin Engines:
1. Briggs & Stratton Vanguard series, both small and big-block designs.
[479-810cc and 896-999cc respectfully]
2. Honda GX series [620 thru 690] and GCV line [520 and 530 - OHC]
3. Briggs & Stratton Intek/XRD and other NON-Vanguard lines
4. Subaru/Robin [FHI] EH line [including EFI models]
5. Kawasaki Twins [691 and others]
6. Tecumseh Enduro line
7. Kohler Courage and Command lines
8. Chinese/no name engines [VARIABLE, some based on honda GX line. These
are good]
Opposed Twin Cylinder Flathead Engines:
1. Briggs & Stratton 14 thru 20hp engines [I believe 40 thru
46cuin/656 - 754cc]
[^ The one, the only..
]
2. Cummins/Onan line [Yeah, Onan is a Cummins engine subsidiary as of 1986]
3. Kohler K-series and Magnum line
Flathead Single Engines:
1. Briggs and stratton 19+cuin models [8 thru 18hp]
2. Tecumseh flathead line
3. Kohler K-series and Magnum line [cast iron black and cyls.] [stronger than tecumseh, harder to find parts]
OHV Single Engines:
1a. Briggs PowerBuilt, I/C, Professional, Intek, and other associated
lines
1b. Honda GX 160 thru 390 [typical repower engines, from 5.5 to 13hp]
2. Tecumseh Enduro line and XL Heavy Duty [OH160 for example]
3. Kawasaki line
4. Kohler line
5. Chinese engines