I have a Stihl chainsaw MS 181 CB-E part number 1139-011-3012 and need to remove the muffler to check the spark arrestor. The bolts holding it on are either a proprietary or security head. Does anyone know what tool is needed to be able to remove the muffler? My assumption is this is to guard against modification.


  • 2
    Could you show us a picture of the bolts?
    – Chenmunka
    Commented Aug 31, 2021 at 10:40
  • A quick search for your model number plus "parts" gave me this page which shows a listing of tools available from Stihl for that saw. Nothing special about a couple of sockets, flat blade screwdrivers or an Allen key/hex wrench. We'll really need a very clear, focused pic of the bolts in question in order to determine if it's really something special.
    – FreeMan
    Commented Aug 31, 2021 at 11:25
  • Google search for muffler removal calls for using a T-27 driver, (a torx screwdriver). Check for yourself incase I goofed.
    – crip659
    Commented Aug 31, 2021 at 11:34
  • I just added muffler removal. The allen keys in your comment link probably are torx type also.
    – crip659
    Commented Aug 31, 2021 at 11:49
  • Photo added for clarity. Commented Aug 31, 2021 at 18:59

1 Answer 1


After staring at my photo for a few minutes I realized these are just plugs. After prying out the plugs the Torx bit presented its self.


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