What is the difference between a 2 and 4 stroke ?

Question by wullymc09: What is the difference between a 2 and 4 stroke ?
I have a new 125 cc pit bike and don’t know if its a 2 or 4 stroke ? It takes staight petrol i know that and there is a oil bit uder my seat ! Anyone know if it is a 2 or 4 stroke ? Thanks

Best answer:

Answer by tom4bucs
two stroke – oil is added to the fuel
only one down-up stroke per cycle

4 stroke – oil is in a separate chamber
takes TWO down and up to fuel the chamber and rid the fumes

all the best

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8 Comments
  1. Reply
    Not just looking for points May 12, 2013 at 4:42 pm

    If there is place to add oil any where either to the engine through a fill cap or a container to just hold oil, it is a four store it doesn’t burn oil with the fuel. But if they told you to mix the oil and the fuel at a certain ratio then it is a 2 cycle motor.

    Also google the VIN number off the frame it will tell you all the info about the bike, or just google the bike name and info and go from there.

  2. Reply
    SHAUN S May 12, 2013 at 4:53 pm

    hi i had a pit bike 110 and mine was 4 stroke and no oil is need to petrol if it sounds like a 4 stroke it is

  3. Reply
    azlbzracer May 12, 2013 at 5:41 pm

    All pit Bikes are 4 strokes

  4. Reply
    guardrailjim May 12, 2013 at 6:09 pm

    For future reference, always give year, make engine size and model # when asking questions. We need all of that info to give an informed answer.

    “oil bit” under the seat, would be an oil tank for 2 stroke oil.
    That oil gets mixed with the petrol by the oil pump.
    A 2 stroke engine will have an exhaust with a big bulge near the engine, similar to this –
    http://www.minipocketrockets.com/mini-dirt-bike-rx1/
    A 4 stroke engine, the exhaust from the engine all the way back to the muffler will be the same diameter.

  5. Reply
    Merlin May 12, 2013 at 6:39 pm

    2

  6. Reply
    The Freak Show May 12, 2013 at 7:14 pm

    GRJ got it 100% right.

    Plus, a 2 stroke has that ring-a-ning-ning chain-saw sound when you rev it up and down. It’s a really distinctive sound and it’s hard to miss.

  7. Reply
    steve d May 12, 2013 at 7:58 pm

    2 stroke and 4 stroke
    The numbers actually relate to the engine cycle of firing or ignition of fuel to create power.

    2 stroke give a power output (1 stroke of power) in 2 engine cranking cycles

    4 stroke give a power output(1 stroke of power) in a 4 times cranking cycles

    Crank turn is 360 degrees = 1 turn

    2 stroke means the crank turns over two times per firing (or power stroke) first turn sucks in fuel second turn compresses and burns (or ignites fuel) and causes a “power stroke”

    2 strokes use a different fuel mix as there are no valves in the engine ignition system (a 2 stroke engine uses a series of chambers staggered in the bore which act like valves)

    4 stroke works on 4 cycles to one “power stroke”

    1 stroke fuel in motor cranks one turn, this is known as induction stroke
    2 nd stroke valves close motor turns crank one turn, this is known as compression stroke,

    3 rd stroke(crank turns one turn) fuel is ignited under load, this is known as the power stroke

    4 th stroke (crank turns one turn) the burnt gases are sucked out of the exhaust this is known as the exhaust stroke

    A four stroke engine has a valve system and uses fuel which is not the same as 2 stroke oil mixed fuels.

  8. Reply
    Goes Without Saying May 12, 2013 at 8:52 pm

    2 Strokes can also be oil injected, so be mindful of that but 2 bikes typically are not oil injected Its most likely a 4 stroke, a 125cc 2 stroke would be a pretty big bike

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