Why do 2-stroke engines produce more HP and torque vs. 4-stroke engines?

For example a stock Honda 250R produces around 39 HP and a Yamaha Raptor 700 produces around 39 HP as well. Why does it take the 700 cc 4-stroke almost 3 times the displacement to produce the same amount of power as the 250 cc 2-stroke?

 

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P.S. more HP yes but not Torque!

 

Thanks. Good reading there.

The other thing which sucks about 4-stroke compared to 2-strokes is how they respond to mods. A good pipe makes a huge difference on a 2-stroke.

 

Look at the motor cross race circuit. It takes a 450 4 stroke to race a 250 2 stroke and a 250 4 stroke to race a 125 2 stroke.

Same with snowmachines,the new big bore 800 4 strokes just keep up to the old 500 2 strokes.

 

And a 2 stroke is so much easier to work on.

The 4 stroke guys may say that you have to rebuild 2 strokes a lot (which I disagree with), but you can redo a top end in no time at all. Try that with a 4 stroke.

 

<div class="FTQUOTE"><begin quote>Originally posted by: Scootergptx

And a 2 stroke is so much easier to work on.



The 4 stroke guys may say that you have to rebuild 2 strokes a lot (which I disagree with), but you can redo a top end in no time at all. Try that with a 4 stroke.</end quote></div>

I agree, I had a on/off road 74 250 2 stroke Honda Esinore motorcycles with 15,000 miles.

My 500 2 stroke ski doo just turned 8,100 miles this winter and still has 125lb in both cylinders.

 

The simple answer is that a 2-stroke has a powerstroke on every cycle, but a 4-stroke only every other cycle.

Don't however be mislead by "horespower" numbers! These are pretty meaningless without seeing a curve that tells you just at what RPM that horsepower gets maid. And why does everybody always post the horsepower, and completely ignore the torque curve????

2-strokes are usually quite "pipey", meaning they make all their horsepower in a limited part of the RPM range. So, if you aren't "in the powerband", the motor can fall flat on its face! What the designers of the current crop of 450's have tried to do, is duplicate 2-stroke performance but keep that broader 4-stroke powerband.

One downside of a 2-stroke, is that I have never met one that was easy to start!

The great thing about the 2-stroke is of course its ultra light weight and simplicity. If Honda reintroduced the 250R, I would have a garage full of them!!!

 

The Honda CR500 had both HP and torgue. Don,t know why Honda never made a 500R.

 

<div class="FTQUOTE"><begin quote>Originally posted by: jt99

Why do 2-stroke engines produce more HP and torque vs. 4-stroke engines?



For example a stock Honda 250R produces around 39 HP and a Yamaha Raptor 700 produces around 39 HP as well. Why does it take the 700 cc 4-stroke almost 3 times the displacement to produce the same amount of power as the 250 cc 2-stroke?</end quote></div>

i also think that if you put a 250r on a dyno it wont even come close 2 making 39hp i whould think it whould be about 30. also another thing to think about is on old quad alot of the time they gave you the hp and the crank not to the ground.

 

Were getting of point,its 4 stroke vs 2 stroke,not 250 vs 450. A 450 4 stroke may have a edge over a 250 2 stroke but look at the cc advantage it needs to do it!

To be proud a 450 can holds its own against a 250 is embarrassing.