Comment Re:Polution? (Score 1) 321
egomaniac said:
I'm sorry, that hasn't been the case for quite some time - they're almost all 4-strokes now. This Link shows that 2-strokes were being phased out under EPA rules as early as 1997. Lawnmower engines are, however, predominately of the flathead or "valve in block" air-cooled style. They have a lower compression ratio than most auto engines and some waste quite a bit of fuel out the exhaust as extra coolant to keep the engine from overheating. The main problem with lawmowers and other small engines, in my opinion, is simple maintenance - or lack thereof. People ignore it so long as it still cuts grass/throws snow/whacks weeds/etc. So it belches a bit of black or blue smoke - still gets the job done and gas is cheaper than a tuneup.
Note, unless it has "OHV" somewhere on the engine it's probably a flathead - overhead valve (OHV) engines are still new enough that they are still worth advertising. Honda makes good ones, and I think Briggs and Tecumseh have at least a few designs on the market. The newer 4-stroke weedwhacker engines are OHV as well, for the better efficiency from the higher compression ratio and better heat rejection.
Have fun,
-cajun
The main reason that lawnmower engines are so incredibly dirty is that they are two-stroke engines.
I'm sorry, that hasn't been the case for quite some time - they're almost all 4-strokes now. This Link shows that 2-strokes were being phased out under EPA rules as early as 1997. Lawnmower engines are, however, predominately of the flathead or "valve in block" air-cooled style. They have a lower compression ratio than most auto engines and some waste quite a bit of fuel out the exhaust as extra coolant to keep the engine from overheating. The main problem with lawmowers and other small engines, in my opinion, is simple maintenance - or lack thereof. People ignore it so long as it still cuts grass/throws snow/whacks weeds/etc. So it belches a bit of black or blue smoke - still gets the job done and gas is cheaper than a tuneup.
Note, unless it has "OHV" somewhere on the engine it's probably a flathead - overhead valve (OHV) engines are still new enough that they are still worth advertising. Honda makes good ones, and I think Briggs and Tecumseh have at least a few designs on the market. The newer 4-stroke weedwhacker engines are OHV as well, for the better efficiency from the higher compression ratio and better heat rejection.
Have fun,
-cajun
