what is the diffrence, 2 and 4 stoke?

is a 4 stroke engine where you put petrol in at a garage, and is a 2 stroke when you mix petrol and oil?????

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  • 1 decade ago
    Best Answer

    you are correct

  • 1 decade ago

    In a 2 Stroke engine as used in motrorcycles and small garden impliments there is no oil sump in the engine ( gearbox/ Transmission has it's own supply). So the engine is lubricated by oil being mixed with the fuel.

    Most modern 2 strokes like your aprilia have a seperate oil tank this MUST be kept topped up with oil the same as you fill your tank with straight fuel. The oil you use is SAE 30 which is sold as T2 or 2Stroke oil.

    So though your bike is a two stroke you DO NOT mix the oil with the fuel, the engine has a pump and a system for doing this in the induction system.

    Basically like any other vehicle you fill your tank with unleaded this is drawn into the carb where it is mixed with the air being drawn into the engine. The air and fuel is drawn into the engine through REED VALVES into the crank case underneath the piston. As the piston reaches top dead centre the valves close and then the piston decends compressing the fuel air mix. As the piston reaches mid point the transfer ports open which allow the fuel air mix to pass from below the piston above it into the combustion chamber. In doing so this forces the remaqins of the burnt exhaust gas out of the combustion chamber into the exhaust expansion chamber. The piston reaches the bottom of the stroke at Bottom dead centre and starts to rise, This compresses the air fuel mix above the psiton and causes a vacuum below and opens the reed valves drawing more fresh fuel in beneath it.

    As the psiton rises the exhaust port is closed and the fuel air mix is compressed further in the combustion chamber At Top Dead Centre TDC the ignition is fired ( well 8 degrees before TDC really) and the spark causes the fuel air mix to burn and expand focing the piston down Starting the cycle all over again. So for one revolution of the engines crank shaft the psiton rises one and decends once performing TWO cycles or strokes UP then DOWN hence the name 2 stroke.

    While all this is going on thwere is a little geared pump attached to the gearcase which is driven by the clutch pack. This pump is fed with OIL from the seperate oil tank. Each time the psiton on the engine goes up a small amount of oil is forced from the pump through pipes and drillings in the casing to the bearings that support the crankshaft and also inot the bearings of the con rod. A small hole in the con rod allows the excess oil to squirt out into the bottom of the piston where it is forced both onto the cylinder wall and to atomise and mix with the fuel and air, in this state it is then circulated inot the compustion chamber where it is burnt with the fuel and ejected out with the exhaust.

    It is a constant loss set up so that oil is being burned with the fuel.

    By mixing oil in the petrol you do not need to have the oil pump and the oil being forced into the bearings as it is fed in with the fuel and air at the same time.

    I hope this helps explain why even though you do not mix oil with your fuel that you have a tw stroke..

    PS a 4 stroke engine has a more complicated lubrication system where the engine has a sump of oil which is circulated round the moving parts by the pump but should not be burnt with the fuel

    There are a lot more moving parts and the fuel is drawn into the enginme through the inlet poppet valve in the cylinder head by the psiton decending. the valve closes the piston rises copressing the fuel air mix It is then burnt, the piston decends and once at the bottom of the stroke the exhaust poppet valve opens and the piston rises forcing the burnt gas out of the cylinder into the exhaust.

    So induction Compression Power Exhuast. Two rotations of the engines crank mean four strokes for one power cycle so hence it is called a four stroke

  • Anonymous
    4 years ago

    Depends on what you had before, were you on a 125? If so, a 250 4 stroke isn't really moving up. Just because they are both 250 doesn't mean they have the same power, a 2 stroke is alot more poweful. You should be trying to decide between a 125 2 stroke or 250 4 stroke, or decide between a 250 2 stroke and a 450 4 stroke. Your not really looking at it from the right perspective.

  • Tim H
    Lv 5
    1 decade ago

    The 4 steps for both engines are intake, compression, power and exhaust.

    In a 2 stroke it is accomplished with one revolution of the crankshaft. So the crank turns 1/4 turn (90 degrees) for each step. On a 4 stroke, its the same . . . intake, compression, power and exhaust but the crankshaft makes two revolutions, so each step takes 180 degrees movement of the crankshaft. That's why 2 strokes have more power readily available, where 4 stroke aren't as responsive when you twist the throttle.

    Hope this helps.

    Source(s): Navy "A" School . . . .
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  • 1 decade ago

    yes and a 2 stroke is more powerful than a 4 stroke of the same cc

    Source(s): dirtbike rider
  • 1 decade ago

    also the 2 stroke is less powerful than the 4 stroke engine

  • Jon P
    Lv 5
    1 decade ago

    The 4 stoke has double stokes and they have oil.

  • Anonymous
    1 decade ago

    You are correct! Here are some animations that may shed light

  • 1 decade ago

    That is one difference

  • Anonymous
    1 decade ago

    OMG ROFL at U some one please help me I have fallen down and I can't quit laffin I think I am going to wet my pants.

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