The best explanation on how a 2-cycle engine works

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I think they're like the Bumble Bee is supposed to be. Impossible.
 
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Truly a light power producing motor. Stupid simple. Produces about 1.5 times the power of the same size four stroke and will run at any angle. I love em, unfortunately environmentalists/ EPA doesn't and they really don't like people like me that encase themselves in smoke. I once argued with a shop teacher in high school because he said two stroke longetivety is shorter than a four stroke. I disagree. Run good oil, at a rich ratio and a two stroke will run as long as a four stroke in the same service.
 
I have always loved the simplicity. I think of them as a pressurized crank area on the down stroke (piston becomes a super charger), then from the bottom of the cylinder the fresh mix pushes out the exhaust. Rinse and repeat.
 
Love the 2 stroke. Light, instant power, very tune-able with exhaust, reed tension, port size and position in the cylinder. And simple. When my boy raced MX, if needed, we could install the spare piston, rings, and cylinder between races. Tuning for short straights and supercross style jumps was done with different pipes and silencer lengths, and race fuels. EPA killed them because of the unburnt hydrocarbon emissions.
Lots more info in Two Stroke Tuning by A. Graham Bell.
https://www.amazon.com/Two-Stroke-Performance-Tuning-Bell/dp/1859606199
One of my best memories is a long ride on a Suzuki GT380, an in line 3 cylinder two stroke.
 
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Originally Posted By: HerrStig
Even with a fancy exhaust and reed valves instead of ports there isn't a lot of low end torque to be had.


You might be surprised at the dyno curves of big bore 2 stroke dirt bikes. 500cc two strokes make a bunch more low end than a comparable 4 stroke. It's a mistake to think that a well designed 2 stroke engine has less low end torque. What really happens is that 125cc two strokes produce almost as much peak power as 250cc 4 strokes. When comparing the two, the 125 falls very short on low end.

Better to compare by displacement.

zm1lw1.jpg
 
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Originally Posted By: HerrStig
Even with a fancy exhaust and reed valves instead of ports there isn't a lot of low end torque to be had.

Normally they aren't tuned for low end torque, but could be. I think also the fact that 2 stokes fire twice as often tends to make people think they are revving higher than they are, compared to 4 stroke.
I used to ride an '84 IT200 (2T) and my buddy had an XR200 (4T) and even off idle my bike was quicker, got a much quicker once on the pipe. The XR would rev out more though, and in the woods the XR had nice and smooth power.
 
Originally Posted By: DoubleWasp
I love 2-stroke outboards. A lot of 4 strokes are just a mess. Lot less to go wrong on a 2.


I don't care what the peanut gallery says, my 2 stroke outboards came out of the hole much quicker than comparable 4 strokers do. My old Polaris jetski would absolutely throw you off if you weren't pretty strong and holding on well when we took off.

Love me a couple strokes...
 
I had 2 Yamaha RD350's that would scream on the street a Yamaha IT465 enduro that had boatloads of torque. Yes a 2stroke can be made for low end torque as the IT465 was exactly that. All the magic happens in the exhaust as the expansion chamber is tuned to use the moving hot gasses volume to PULL in the fresh fuel charge. The misconception of peaky horsepower IMO came from dirt bikes that were always run on the ragged edge around a track.
 
And the two stroke methodology really shines in something like the OPOC engine that has been developed. I can only hope that they start showing up in cars and trucks before I croak. The Chinese have already invested heavily in the design. Opposed pistons with opposed cylinders and supercharged along with direct injection. But two stroke, nonetheless.

http://ecomotors.com/opposed-piston-opposed-cylinder-engine
 
Originally Posted By: TiredTrucker
I can only hope that they start showing up in cars and trucks before I croak. The Chinese have already invested heavily in the design. Opposed pistons with opposed cylinders and supercharged along with direct injection. But two stroke, nonetheless.


You can die happy...they've already been commercialised before
 
I have been there when they sail away with those monsters - don't look very clean burning ...
 
Originally Posted By: Kawiguy454
I had 2 Yamaha RD350's that would scream on the street a Yamaha IT465 enduro that had boatloads of torque. Yes a 2stroke can be made for low end torque as the IT465 was exactly that. All the magic happens in the exhaust as the expansion chamber is tuned to use the moving hot gasses volume to PULL in the fresh fuel charge. The misconception of peaky horsepower IMO came from dirt bikes that were always run on the ragged edge around a track.


Yes. I had a radical flat track 305 that would sputter up to 6000 rpm or so and then start pulling the front wheel as fast as you could grab gears. No low end at all, when I started it in the morning I sprayed starting fluid into it for the first 1/4 mile. But great fun on the street, ran right with a new 900 Kawasaki!
 
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