How does a 2 stroke compare to a 4-stroke?

Given all the gripping back and forth on 2 strokes on non related threads, I thought I would start a new thread so every one can duke it out here. The one good thing is, now I know way more than I ever wanted to about a two strokes. :banghead:

Here a link if anyone want to know how they work:

http://science.howstuffworks.com/two-stroke1.htm

Two strokes rule. Awesome power. Without all the noise. :banghead:

4 strokes may be louder, but at least they sound good. On the two stroke side, they smell wayyy better. Love that premix scent.

4 strokes may be louder, but at least they sound good. On the two stroke side, they smell wayyy better. Love that premix scent.

]

Ahh yes, nothing beats the smell of VP C12 and some Klotz...needs to be an air freshener. And I was watching some old videos the other day and the sound of the 125 start (when there were only 125's) was phenomenal. I remember watching pro 125 races in awe as the pipe glowed blue and the motor was revving at 280000000rpm

:banghead:

man two strokes are lighter and like got better acceleration....but for places like here they are obsolete because you got to hold them wide open to get them to climb a hill....i still love my blaster though. haha

they don't compare... apples and oranges...

one is not better... one is merely different, and both have superb applications for specific environments...

I'd rather rebuild a smoker top end than a thumper... :banghead:

Engine test - circle the correct answers:

I can't believe anyone actually rides a (two stroke, four stroke)! (Two strokes, four strokes) totally rule! I have a (two stroke, four stroke) and it totally kicks the (two stroke, four stroke) out of my buddy's (two stroke, four stroke)! Seriously! Only a total moron would ride a (two stroke, four stroke)! All you losers who ride a (two stroke, four stroke) will always lose to me and my all-conquering (two stroke, four stroke)! (Two strokes, four strokes) 4 eva!

man two strokes are lighter and like got better acceleration....but for places like here they are obsolete because you got to hold them wide open to get them to climb a hill....i still love my blaster though. haha

Two strokes obselete for hillclimbing?!?!?! My 500 will climb anything that has tire tracks on it. It will Idle up cliffs, I've only had it wide open once up a hill, and that was because I was in first gear and I was going to slow to make it without spinning the tire and flopping. Buy yourself a 1984 500, and throw that engine in your blaster. You will have the best power to weight ratio out of all your friend's quad's, and nothing will be able to run with it.

I just don't understand what the fuss is all about. I like riding any of them, 4 strokes, 2 stroke and no strokes. I've been riding and working on bike since I was 10. I am now 47. I still get enjoyment anytime I sling a leg over anything that will pull my old butt around. I don't even mind taking either down, when works needs to be done. All of them have their pluses and minuses. I cannot knock either.

I just don't understand what the fuss is all about. I like riding any of them, 4 strokes, 2 stroke and no strokes. I've been riding and working on bike since I was 10. I am now 47. I still get enjoyment anytime I sling a leg over anything that will pull my old butt around. I don't even mind taking either down, when works needs to be done. All of them have their pluses and minuses. I cannot knock either.

I'm not saying I dont like thumpers, I've owned 2, I just hate rebuilding them, there is too much stuff in there! :banghead: Rebuilding the top end on a thumper is like splitting the cases on a pinger. It may be worse actually, there are around 28 bolts required to take apart the top end of a WR400. That's a whole lot of turning bolts. I sold my 400 because it was such a pain to work on. I liked riding it though. 2strokes are fun, 4strokes are easy to ride, but I'm faster on a Pinger (atleast when it's a well running 1/2 liter :banghead: ). To each his own, I've had both, I like the 500 for play riding, and I liked the WR400 for when it got into the tight slow technical trails, because it had a lower first gear. They both got the job done, just one is cheaper to maintain, but slightly harder to ride.

I hear you 99WR. I guess I'm just an oddity. I like turning wrenches. LOL

Engine test - circle the correct answers:

I can't believe anyone actually rides a (two stroke, four stroke)! (Two strokes, four strokes) totally rule! I have a (two stroke, four stroke) and it totally kicks the (two stroke, four stroke) out of my buddy's (two stroke, four stroke)! Seriously! Only a total moron would ride a (two stroke, four stroke)! All you losers who ride a (two stroke, four stroke) will always lose to me and my all-conquering (two stroke, four stroke)! (Two strokes, four strokes) 4 eva!

Man, that just about covers it as for as the pissing contest is concerned.

I raced my CR125 all year and it got to the point where I would just wait for all the 4-strokes to get off the line and follow them into turn 1 because I would get run over if I tried to get a good start.

About a week ago I got to ride a KXF250 and I was floored at what a 250F can do. I want to buy a CRF250x (with e-start) now and sell my 125.

The only downfall to 4 strokes that I can see is the weight, Maybe a few more gyroscopic forces (more rotating mass) and the fact that you can go from first place to 2 laps down because you can't get the bike started after you stall it or crash. I don't know how often I saw that this year and every time I thought I bet that guy wishes he had a 2 stroke.

My son started out on an XR80. We ride the tight single track in mountainous NorCal. When he got good enough, he HAD to have a CR85. What kid doesnt. He owned it for 9 months and hated it. I tried everything I could to modify it to make a good trail bike; gearing, Steahly flywheel, lower compression head. Now 12, he rides an XR200 and loves it. Each has their place. Tight, techincal woods with gnarly uphills punctuated by rocks and tree roots are not the domain of the small bore two stroke. But try telling an 11 year old that.

man two strokes are lighter and like got better acceleration....but for places like here they are obsolete because you got to hold them wide open to get them to climb a hill....i still love my blaster though. haha

I took my ATC 250R to the Hatfield-McCoy Trail System in WV this summer and had a killer time. Those mountain trails were just the ticket to light up my two-stroke. It pulled strong in all gears, I did miss the engine braking on the way back down the mountain. More fun than a barrel of monkeys. I'm building up my boy's CRF 100F to tackle H-M on next summer's trip.

what i was saying is like when you want to creep around realllly slowly like up hills you kinda cant on a two stroke or it dies....id ride anything that will pull me i really dont have a problem with 2 strokes but im tryin to get a YZ450 engine to go into the blaster frame though

Both two strokes and fourstrokes are great bikes when used for different purposes and in different situations . Some people are two stroke lovers and some people are fourstroke lovers . As far as I can tell , the name Thumpertalk means that this is a site for 4 stroke fans to get together and talk about fourstrokes . I am a fourstroker through and through but I also don't mind 2 smokes , it's just that they've let me down in the past despite being carefully serviced and maintained . I am just pointing out the facts about the differences between both types of engines mainly so that people who don't know and want to know might learn something new and interesting ! To get uppity and defend twostrokes on a fourstroke site is akin to a gay man infiltering a hetero site to extoll the virtues of the gay lifestyle . This could tend to leave a foul and bitter taste in the mouths of hardened fourstroke fans !

As far as racing goes there are several reasons why two strokes are cheating against 4 strokes on a naturally aspirated playing field even if the air/fuel capacity and burn rate is equalised ! If you think they're not cheating , take one of these tests ----- iqtest .com -- tickle super iq test -- or any other test and you'll soon find out why you can't see it . The rules have to be adjusted to suit 2 strokes despite the fact that they induct and combust more than twice the amount of air/fuel capacity at well above atmospheric pressure , of a comparable 4 stroke , purely because they are far less efficent at turning their combustion force into rear wheel horsepower and torque than a 4 stroke engine design . Two strokes have the downfall of severe frictional power losses and their port design allows combustion pressure to escape before it has been fully utilised to maximum effect . Anyone disputing this fact on friction should drain all the oil out of their 4 stroke engine or gearbox on their 2 smoke and replace it with two stroke mix , I dare you !!!!!!!! The real amount of power that two stroke engines produce before friction loss is staggering and would be well over that of a 4 stroke burning the same air/fuel per rev . Because of these facts , it will be no longer appropriate to refer to any MX racing class as the 85 , 125 or 250 class . Here's a suggestion ------ The apples and oranges class or the 10 % handicapped class .

The rules in road racing and drag racing are : A 2 stroke engine must race a double the capacity naturally aspirated 4 stroke or a supercharged 4 stroke of the same capacity .

Two-stroke engines fire once every revolution, while four-stroke engines fire once every other revolution. This gives two-stroke engines a significant power boost.

Two-stroke engines also have the potential to pack about twice the power into the same space because [ there are twice as many power strokes per revolution ]. The combination of light weight and twice the power gives two-stroke engines a great power-to-weight ratio compared to many four-stroke engine designs.

You can now see that two-stroke engines have two important advantages over four-stroke engines: They are simpler and lighter, and they produce about twice as much power.

POINT 1) --[ Two strokes suck in and burn TWICE the air/fuel capacity as the same capacity fourstroke engine }

Fuel Intake

As the piston finally bottoms out, the intake port is uncovered. The piston's movement has [pressurized the mixture in the crankcase, so it rushes into the cylinder], displacing the remaining exhaust gases and filling the cylinder with a fresh charge of fuel .

The Compression Stroke

Now the momentum in the crankshaft starts driving the piston back toward the spark plug for the compression stroke. As the air/fuel mixture in the piston is compressed, a vacuum is created in the crankcase. This vacuum opens the reed valve and sucks air/fuel/oil in from the carburetor.

Once the piston makes it to the end of the compression stroke, the spark plug fires again to repeat the cycle. It's called a two-stoke engine because there is a compression stroke and then a combustion stroke. In a four-stroke engine, there are separate intake, compression, combustion and exhaust strokes.

You can see that the piston is really doing three different things in a two-stroke engine:

* On one side of the piston is the combustion chamber, where the piston is compressing the air/fuel mixture and capturing the energy released by the ignition of the fuel.

* On the other side of the piston is the crankcase, where the piston is creating a vacuum to suck in air/fuel from the carburetor through the reed valve and then ---* [ pressurizing the crankcase so that air/fuel is forced into the combustion chamber.]*

* Meanwhile, the sides of the piston are acting like valves, covering and uncovering the intake and exhaust ports drilled into the side of the cylinder wall.

If you have ever used a two-stroke engine, you know that you have to mix special two-stroke oil in with the gasoline. Now that you understand the two-stroke cycle you can see why. In a four-stroke engine, the crankcase is completely separate from the combustion chamber, so you can fill the crankcase with heavy oil to lubricate the crankshaft bearings, the bearings on either end of the piston's connecting rod and the cylinder wall. In a two-stroke engine, on the other hand,----*[ the crankcase is serving as a pressurization chamber to force air/fuel into the cylinder ] *, so it can't hold a thick oil. Instead, you mix oil in with the gas to lubricate the crankshaft, connecting rod and cylinder walls. If you forget to mix in the oil, the engine isn't going to last very long!

POINT 2) -- *[ A supercharger or Turbocharger is also a pressurisation chamber designed to mechanically force air/fuel into the cylinder so --- forced induction means that two strokes are mechanically supercharged from the intake side ]

Fuel Intake

As the piston finally bottoms out, the intake port is uncovered. The piston's movement has pressurized the mixture in the crankcase, so it rushes into the cylinder, displacing the remaining exhaust gases and filling the cylinder with a fresh charge of fuel, as shown here:

How Two-Stroke Expansion Chambers Work, and Why You Should Care.

By Eric Murray

You know that changing the exhaust pipes on your two-stroke motorcycle can have a marked effect on the engine's power characteristics, but do you know why?

Simply put, it's because the two-stroke exhaust system, commonly referred to as an 'expansion chamber' uses pressure waves emanating from the combustion chamber to effectively supercharge your cylinder.

In reality, expansion chambers are built to harness sound waves (created in the combustion process) to first suck the cylinder clean of spent gasses--and in the process, drawing fresh air/gas mixture (known as 'charge') into the chamber itself--and then stuff all the charge back into the cylinder, filling it to greater pressures than could be achieved by simply venting the exhaust port into the open atmosphere. This phenomenon was first discovered in the 1950s by Walter Kaaden, who was working at the East German company MZ.

POINT 3) -- Two strokes are further supercharged by the expansion chamber , so not only do they induct and burn air/fuel at twice the rate of a 4 stroke of the same bore capacity , they also get that double capacity mechanically forced into the cylinder by the downward force of the piston and then on top of that they are double supercharged through the exhaust port via sound pressure waves in the expansion chamber . If that aint cheating I don't know what it is . STREWTH !!!!!!!!!!!!!!!!!!!

If an athlete " supercharges " themselves above and beyond the norms of nature with amphetamines and steroids , then wins an Olympic event or any event of any type , everyone cries cheater and disqualifies and bans them for life . In fact if they test positive for drugs they get disqualified and banned even if the are uncompetitive . If you agree that athletes are cheating by using steroids then you would be a hypocrite for thinking twostrokes are'nt whether they are competitive or not !

POINT 4) -- It would pay for some people to " SUPERCHARGE" their brain with facts then make sure it's shoved it into overdrive BEFORE dumping the clutch on their mouth (or should I say fingers ) only to valve bounce in NEUTRAL !!!!!!!!!!!!!!!!!!

There was NO pissing contest , just an Aussie getting badgered by a couple of Yank wombats !!!!!!!!!!!!!!!!!!!!! :lol::banghead::banghead: :crazy:thumbsup: :busted:

what i was saying is like when you want to creep around realllly slowly like up hills you kinda cant on a two stroke or it dies....id ride anything that will pull me i really dont have a problem with 2 strokes but im tryin to get a YZ450 engine to go into the blaster frame though

My 500 will idle up anything. It's only limitation is traction. It will chug up anything better than any thumper will. It's like a diesel. It just chugs! Put a 490 engine in the blaster instead, it would be cooler, cheaper, faster, and easier to ride.

Quote:

Originally Posted by Yamiha

what i was saying is like when you want to creep around realllly slowly like up hills you kinda cant on a two stroke or it dies....id ride anything that will pull me i really dont have a problem with 2 strokes but im tryin to get a YZ450 engine to go into the blaster frame though

Have you seen a two stroke trials bike ? They're known as the mountain goats of the motorcycle world and will just about climb a brick wall with ease !

they don't compare... apples and oranges...

one is not better... one is merely different, and both have superb applications for specific environments...

I'd rather rebuild a smoker top end than a thumper... :banghead:

I second everything you said :banghead:

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