I am buying a scooter soon and dont know much about the technical... please help
Here is what Wikipidia has to say about it: Two-stroke engines are mechanically simple and can produce more power from lighter mechanicals than four-strokes, having twice as many power strokes at the same engine revolutions. Their acceleration is significantly better than an equivalent four-stroke even when their top-speeds are similar. They are easier to start. Their fuel inefficiency seemed a small price to pay to their devotees, who were many. Even their generally shorter life (linked to marginal piston lubrication) was not a serious impediment and plug-fouling was a distant memory, a thing of the past. Four-strokes are generally associated with a wider powerband making for somewhat gentler power delivery.
Down side to two strokes is 2-cycle engine oil has to be mixed in with the gas. A lot of newer 2 stroke motorcycles have a oil reservoir that mixes the oil for you, but I have been told that those go bad fairly easily, then you are running around with no oil and the motor burns up. Because of that most people I know rip those off and mix their own oil & gas. Also, even tho they are mechanically simple- I have been told they break down a bit more. So they are good for people who can repair their own bikes. Also, 2-strokes I find are usually louder - they sound a lot like a chain saw :p.
4-strokes are going to be more like your average car - needed gas and oil separately - and they pretty much take regular motor oil. They are much more mechanically complex than a 2 stroke, but overall I hear they are more reliable. The wider power band on them can be very nice for highway cruising.
My friend has said the next bike he gets is going to be a 4-stroke because he is tired to screwing with 2-strokes and having troubles with them.
Now all this I know is referring to motorcycles, but as far as I know scooters use more or less the same motors.
everyone else pretty much covered it. with a 4 stroke, the spark plug only ignites on 1 out of every 4 times the piston goes up and down. with a 2 stroke it is 1 out of every 2. therefore, as far as a scooter goes, you can have a smaller motor, lighter scooter but have the same power as a larger and heavier one that has a 4 stroke. typically this is how it works. manufacturers will not give you an engine the same size as a 4 stroke thus giving you much more power, instead they'll give you a smaller engine with about the same power as what a larger 4 stroke will have. check horse power ratings when comparing the two.
everyone is also correct about the oil. mixing the oil with the gas is not a big deal, but it is one more thing to have on hand and can sometimes be a pain in the neck. you can get gas anywhere but you can't buy the 2 stroke oil anywhere (it isn't regular motor oil). so depending on accessibility, this can be a deterant to a 2 stroke.
the other thing about a 2 stroke is that they can easily be run on their sides or upside down (which is why, along with their lighter weight, you find them on things like chain saws, leaf blower, hedge trimmer, etc, things that may be turned on their sides a lot). this is because with any 4 stroke, there is an oil pan on the bottom of the engine where the oil is stored for the engine. if that is turned on its side, the oil runs into places where it doesn't below and leaves places it does belong, causing all kinds of problems.
all things considered... unless you live in an area where there are a lot of farms or logging, i would go with the 4 stroke as there will be a day where you run out of oil for a 2 stroke and can't get any more easily.
When I was young the majority of motorcycles were 2 stroke. Nicer 2 stroke engines didn't require mixing oil with gasoline but injected oil directly where it was needed for lubrication rather than mixing it with gasoline. These engines still burned oil but much less than when oil was mixed with the fuel. Most modern 2 stroke marine engines still use this system.
All 2 stroke scooter engines I'm aware of require you to mix oil with your fuel. Chances are a 4 stroke engine will be more reliable and durable than a 2 stroke but 2 stroke engines are much simpler and easy to repair. If you are going to perform your own repairs this can be a big advantage.
I went and did a little research for you, heres what i found that might help your decision. Two stroke engines are lighter and cheaper to manufacture so in turn they will be cheaper to purchase. However, since they arent manufactured as well and with as much technology as a 4 stroke engine they dont last as long in the end. Two strokes also get less miles per gallon of fuel, and oil needs to be mixed in everytime you fuel up. This leads to more oily smoke being emmited from the scooter than a 4 stroke.
In the 1970's I rode a 2 stroke Kawasaki and a 2 stroke Bridgestone motorcycle. Both had oil injection and I never had any trouble with either. Each held 1 qt of oil which was enough for many refills of the gas tank. I've had cars that burned more oil.
How has your luck been with the oil being directly injected in with the 2 strokes? I have heard those are not very reliable, and everyone I know rips them out and just mixes the oil and gas themselves.
4 stroke is better.....yeah