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Piston Replacement Stihl MS 180

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  • 13-10-2009 9:03pm
    #1
    MKEOGHAN
    Registered Users Posts: 37 ✭


    Hi I need help. I was told that my Piston needed to be replaced. I have stripped my Stihl MS 180 chainsaw down to its bare body. I cannot however remove the Master cylinder. I seems to be attached to the flywheel and power brake on the blade side.

    Any help on how to remove this would be great.

    Regards,
    Michael


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    #2
    CJhaughey
    Registered Users Posts: 14,907 ✭✭✭✭CJhaughey


    To remove the cylinder you need to undo the 4 bolts that are on the bottom 4 corners of the cylinder, I can't remember what they are but many of the Stihl fasteners are T27 Torx.
    Remove the Carb and inlet manifold as well.
    The cyl should lift straight off.
    Is the saw clean enough? You don't want dirt and crap falling down into the crankcase when you pull the cylinder off.
    What happened? Straight petrol or just a worn piston? You may find that if there has been a partial seizure from bad mix that the cylinder is smeared with aluminium from the piston. You will need to use acid to remove the aluminium if this is the case.


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    #3
    MKEOGHAN
    Registered Users Posts: 37 ✭MKEOGHAN


    The cyl should lift straight off.

    This is as far I could get. The four bolts are removed, Carburettor inlet boot removed. But the cylinder will not lift up. It wants to take the flywheel with it!.. The Flywheel and power break are both moving with the cylinder??????

    Saw is very clean.


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    #4
    CJhaughey
    Registered Users Posts: 14,907 ✭✭✭✭CJhaughey


    Your saw sounds like it is siezed, the piston has got stuck in the cylinder.
    Could you pull it over before you started dismantling it or has it just got stuck since you started?
    How do you mean the flywheel and clutch are moving? Are they rotating or are they pulling up and down vertically?
    Don't twist the cylinder, those MS180 conrods are weak stamped steel.


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    #5
    MKEOGHAN
    Registered Users Posts: 37 ✭MKEOGHAN


    Piston is moving no problem. No visable scores inside. Top of the piston is fine also. The cylinder head is lifting the Flywheel and the Power break on the other side. I cannot lift the cylinder head without it trying to them also. I dont want to force it. All bolts are removed!

    Thanks


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    #6
    CJhaughey
    Registered Users Posts: 14,907 ✭✭✭✭CJhaughey


    The Ms180 is a clamshell design, meaning that the crankcase is a metal insert inside the plastic the cylinder is bolted to the metal crankcase.
    The whole cylinder and crankcase lift out. and underneath the crankcase is 4 bolts that when you undo and give the crank a light tap the bottom half can be removed.
    Pull the crank and piston assembly and replace.
    You have to pull the flywheel and clutch off before you go at the rest!


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