Ever notice what happens to oil on a metal surface when you pour gasoline on it? Oops! Seems like the gas and oil in a two stroke are quite at odds with each other. The gasoline wants to break down and rinse the oil off the surfaces it's trying so very hard to lubricate!
According to Lhead :
Sigh.
You know, I don't expect everyone to have taken not one, but two small engine repair courses as I have and intimately know the details of how four stroke and the three types of 2 stroke engines work, but at _least_ you should know the difference between having a _bath_ and having a _shower_.
The oil-gas mix in a two stroke is atomized in the carbureter, and pulled thru the crankcase and thence to the intake port. Thus, the insides of the motor are showered with a gas oil mix, and the oil is then run thru the cylinder head and (partially!) burned before being dumped into the atmosphere.
As for example, the pilots of certain aircraft in world war one were continuously sprayed in the face with a partially burned laxative (they used castor oil in those days).
Meanwhile, in a four stroke, the crank and cylinder head is mostly isolated. The oil is in a _bath_ at the bottom of the crankcase, and the crank, and bottom end of the piston rod splash (and to a certain extent are bathed _in_) the oil at the bottom of the crank. The oil _stays_ in the engine and doesn't spray anyone in the face.
So, no, a 2 stroke doesn't bathe its parts in oil. But a 4 stroke does.
Chris Lewis wrote:
I didn't realize I was dealing with an "expert". You know, I've never had my Lawnboy or any two stroke engine spray oil in my face. Maybe it's a common occurance and I just hasn't happened to me. Hmmm. Actually, the oil in a four stroke Briggs/Techumseh style engine resides in what's known as a sump. In engine terminology, the sump is the area below the crankshaft in a four stroke. In cars, the sump and the oil pan are one in the same. That is for wet sump engines. Dry sump engines have an external oil tank and feed and return lines leading to and from the oil pump. An oil "bath" on the other hand was how air cleaners worked in the days before disposable paper elements. So Chris, knowing 'intimately' how small engines work, answer a question for me: If the two stroke engine doesn't bathe its parts in oil, how on earth does the engine get lubricated? How has my Lawnboy lasted twenty years now without siezing up? You know, I would think that lubrication would be vitally important in two strokes, given that many of them turn between 10,000 and 20,000 RPM routinely. You stated that the insides of the two stroke are showered with the gas/oil mix, but not bathed. What's better, a shower or a bath? Here's what I know. I've had both Techumseh and Briggs engines throw rods and punch holes in crankcases. Any yes, I've changed the oil according to schedule. The newer Tec/Briggs lower end engines especially can be considered throw aways after a few years of service. My Lawnboy, on the other hand has gone twenty years without any major repair work of any kind. And that's cutting a half acre twice a week.
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