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Stihl MS311/391 Port Cover Removal

Discussion in 'Chainsaw' started by magicmanar98, Feb 13, 2020.

  1. magicmanar98

    magicmanar98 ArboristSite Lurker

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    Has anybody successfully removed the port covers on the stihl MS391/311 cylinder? I’m not sure how stihl seals these things on but they’re on there. There’s gotta be a way but I haven’t found it. I appreciate any input. Thanks
     
  2. alexcagle

    alexcagle Cutoff Saw Specialist

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    I re-glued one that had popped loose with yamabond #4 a year ago that is still holding......;);)
     
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  3. Justin Taylor

    Justin Taylor ArboristSite Guru

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    What are you planing on doing?
     
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  4. alexcagle

    alexcagle Cutoff Saw Specialist

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    Cleaned it first several times with lacquer thinner though.
    The cylinder was off the saw, and I put it in my oven at 120º overnight. It's probably high heat epoxy.
     
  5. magicmanar98

    magicmanar98 ArboristSite Lurker

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    I had one pop off too, but the other I can’t get to budge. Been chipping aluminum off working the other side.
     
  6. magicmanar98

    magicmanar98 ArboristSite Lurker

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    Dremel transfers to open it up a bit. I’m pretty good porting intake and exhaust. Not so much on transfers. Covers off will make it easier. I’ve got a machinist at work gonna drop cylinder .020” as stock squish measured .040-.045”.
     
  7. magicmanar98

    magicmanar98 ArboristSite Lurker

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    I put a heat gun on it and it didn’t phase it. The one that came off of one side of mine looks like liquid steel or they got the aluminum to bond to each other somehow.
     
  8. Justin Taylor

    Justin Taylor ArboristSite Guru

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    Dropping the cylinder on a clamy I need to see some pics
     
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  9. magicmanar98

    magicmanar98 ArboristSite Lurker

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    I will this time. If I can ever get this darn cover off! Not gonna try it on new 391 cylinder until I figure out a good way on this 311 cylinder.
     
  10. rupedoggy

    rupedoggy Addicted to ArboristSite

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    Huskybill says just take .020 of the cylinder then .020 off the top of the bearing race and seal LOL
     
  11. Justin Taylor

    Justin Taylor ArboristSite Guru

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    :lol:
     
  12. Justin Taylor

    Justin Taylor ArboristSite Guru

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    And porting a 311 would be a pain in the ass I think
     
  13. Justin Taylor

    Justin Taylor ArboristSite Guru

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    Btw there is a pop up piston for the 391 if you didn’t already know
     
  14. rupedoggy

    rupedoggy Addicted to ArboristSite

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    Oh don't tell him that. He was doing so good without it.
     
  15. Justin Taylor

    Justin Taylor ArboristSite Guru

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    Let’s just hope he doesn’t need it
     
  16. magicmanar98

    magicmanar98 ArboristSite Lurker

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    Oh no! I gotta have it. Might as well just cut squish to .010”-.012” and see if I can get the piston to fly through the clouds.
     
  17. magicmanar98

    magicmanar98 ArboristSite Lurker

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    My dealer said it took 3 tanks of straight gas to lock the 311 motor up, so who knows, the sky’s the limit
     
  18. Justin Taylor

    Justin Taylor ArboristSite Guru

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    The wrist pin shaved like .030 because the cir clip fell out and it dosent even care on my 311
     
  19. magicmanar98

    magicmanar98 ArboristSite Lurker

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    What kind of bar and chain setup are you using on your 311?
     
  20. Justin Taylor

    Justin Taylor ArboristSite Guru

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    20 3/8 .050
     

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