Originally Posted By: Cujet
Originally Posted By: 1999nick
The above figures are not how long an engine will last. They are just how long they are expected to remain in emissions compliance. A well maintained (i.e., frequent oil changes) engine should last several times the above figures.
Yes, that might be true. But the facts remain, cheap engines fail to run cleanly for very long, they simply wear out. The EPA testing is quite informative. As I mentioned, it's an easy way to determine eng quality and expected lifespan. The testing has already been done for you.
Also, the EPA compliance hours allow for degredation of emissions over the lifetime of the engine. By the time the test is over, the engine (maintained by the manufacturers schedule, btw), the engines are considered worn out. They are likely smoking at startup and running rough at idle.
While ancedotal stories will never be admissable as proof, All of my consumer grade engines have exponentially exceeded the EPA emission figures. I agree it may indicate a quality of build, and I have no clue as to unseen emissions. But I disagree that they wear apart. I would argue they fail emmisions for maintenance the average homeowner is not willing to do. I have antiques that start immidiately, run flawlessly and operate without smoking. I have machines fall apart around their engines, both two and four cycle.
What causes them to come out of emission compliance? I love a rebuild, but usually a carb cleaning, oil change and valve adjustment is all that is ever needed to keep simple air cooled engines operational. The tolerances are wide, and wear is rarely an issue. I rarely find valve or seat issues other than adjustment. The mufflers are cans, not cats. A failing breather might allow oil in to be burnt in combustion, but are an easy 5 minute switch Is it carbon build up on the head, that is never removed? I will admit that is a more involved maintenance procedure.
I understand that the average consumer will not adjust valves, carbs, change a breather or scrape a head, but that does not mean the engine wore out in 250 hours or 5 years.