DAVID - I did oil analysis on a K241 10 HP Kohler about a year or so after I rebuilt it. In the fall I changed the oil and put the snow blower on. Blew snow several times that winter... did three drives most times. That spring with maybe ten hours on the tractor I pulled the blower off and put the mower on and started mowing. Early-mid May I get a call from my buddy...."can you come over with your tractor?" He had a HAY FIELD for a back yard at his new house. He'd bought a repossessed house and they'd mowed the back yard twice with a farm tractor the year before, the clippings from that were still there plus the grass was already over a foot tall. Took me close to an hour to make the first round taking a full 38 inch cut... second round taking about 10-12 inch swath I started hearing a slight knock or ping. I stopped, idled the engine around 1800 RPM for ten minutes, no smoke, no more knock... went back to work with just a bit less vigor... took a 6 inch swath each pass. Finished up mowing and had TWO flat tires from junk hidden in the grass.
Called around and found a place that had used oil test kits, sent in a sample to the lab. The oil had about 20-25 hours on it. The results came back with No unusual wear metals (good news) but the amount of un-burned gasoline and water in the oil was off the charts. The un-burned gas from blowing snow in the winter and the oil not getting hot enough to boil the water condensate out of the oil. In cold winter temps an air cooled engine is over-cooled. But in hot summer (90+ deg F) with a full load an air cooled engine can get VERY hot, I'd expect to see 300+ degree oil temps. Dave Kirk rigged up an electric oil temp gauge for his Killer Kohler K301 (12 hp) and I forget exactly how hot he saw his oil get... I'll have to search another forum for that info... but it was more than 230 degrees... a LOT more.
Ha-Ha.... have to agree with the poor combustion chamber designs on these old Kohler & Onan's.
Yes, the Fed. gov't killed 2-strokes... I bought an RD-350 Yamaha right after I got out of college... REALLY enjoyed that bike... but street riding scares the heck out of me anymore. My Buddy had a Penton 125 with a European engine, DKW or Sachs? had HUGE cooling fins... he cold seized that engine twice while riding slowly around difficult terrain, then pulling out onto a road and running up to 60-70 MPH... it would seize by the time it got to 70. UNLESS you pulled the choke half way out to de-tune performance. The Honda's, Suzuki's, Kawasaki's, even my OSSA never had a problem like that!
A water-cooled 2 or 4-stroke wouldn't either.