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ms170 compression

Discussion in 'Chainsaw' started by Nathan Graff, Apr 13, 2019.

  1. Nathan Graff

    Nathan Graff ArboristSite Member

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    So, I changed the carb on the MS 170, and expanded the muffler opening a bit. Now, I can't get the saw started. I tried giving the saw sniffs of carb cleaner to get it going. However, it wouldn't even stutter. I have spark, the air filter is new. I cleaned the case all up. fuel lines seem to be ok.

    So, I put a compression tester on it, and I couldn't get more than 85-90 psi out of it. And I heard hissing sounds from around the cylinder somewhere. Any ideas where to start, or should I go get a used Husky 340, or stihl ms260?
     
  2. Colt Marlington

    Colt Marlington ArboristSite Guru

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    Lots of guys here like the 260.
    Quite a difference in size/feel of saw over a little 170 though.
    My 50, 60, and 70cc saws have their place, but I have a few small saws that I like to use a lot.
     
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  3. jltrent

    jltrent ArboristSite Operative

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    If that compression is right on the 170 then Houston we have a problem. Remove the muffler and take a look. IF the piston is not smooth then the saw is ready for a rebuild or parting out. If smooth then the carburetor you put on is suspect. The carbs on these have one adjustment and are either right or you can't make them right. The Husky and Stihl you mentioned are good.
     
  4. Nathan Graff

    Nathan Graff ArboristSite Member

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    I've always had a hard time starting this saw cold. Lots of pulling the cord, and sometimes giving it a sniff of something to get it going.

    When I had the muffler off to do that mod, it looked ok. But, I"ll take it off again and have a look. And I'll pull the carb back off and see what it looks like. I put a carb from a MS 230 onto this saw so I could adjust it.
     
  5. Snowchaser

    Snowchaser ArboristSite Operative

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    Just did the same to mine today. Not sure about the 230, but the wt215 carb i bought, i had to drill out the brass plug and plug up the port next to it so the factory impulse port would line up. Also plugged the intelli port in the air box to keep junk out. Thing fired right up and runs better than it ever has after a little high/low adjustment. Thanks to blsnelling’s directions posted on this a while back.
     
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  6. dougand3

    dougand3 Addicted to ArboristSite

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    Multiple issues here. As snowchaser indicated....if you put an MS250 carb on it - the impulse hole is at 2 o/c. You need 12 o/c. If it's really 85 PSI, it ain't gonna run. Lay off the sniff squirts - use fuel mix in plug hole or carb throat. Sniff is washing lube off piston, ring and cylinder. If done frequently, p,r and c are scored. An AM topend is $20 or a whole engine drop in is $28.
     
  7. Nathan Graff

    Nathan Graff ArboristSite Member

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    Can a bigger topend be installed?

    It was a walboro 215 carb. And I did pop out the brass plug at the top.
     
  8. dougand3

    dougand3 Addicted to ArboristSite

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    MS180 is 38mm & 32cc over MS170 at 37mm & 30cc. Either will fit.
     
  9. Nathan Graff

    Nathan Graff ArboristSite Member

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    Is it possible to climb into the 210 or 250 p/c class?
     
  10. dougand3

    dougand3 Addicted to ArboristSite

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    No, MS210 230 250 are a bigger series.
     
  11. Nathan Graff

    Nathan Graff ArboristSite Member

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    So, I took the muffler and the carb off the saw. The impulse hole on the carb was plugged. So, I cleared that out, and cleaned up the mating surfaces. The piston and rings were fine. Put the saw back together. It started on the 6th or 7th pull. Really good considering that if the saw had no gas in the line, it would be a half hour ordeal to get it going previously.

    Seems to be cutting faster with the muffler opened up, and the newer carb tuned in.
     
  12. rd35

    rd35 Just an average Joe's brother!!

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    Hmmm….I guess that impulse port really is important! :D Congrats on getting it running. I just love those little saws. Nimble and stout! Great for limbing out the top of a tree when cutting firewood! I like to toss my 018 behind the seat of my pick-up truck after a storm. Comes in handy to cut trees and limbs out of the road as I head to town!
     
  13. anlrolfe

    anlrolfe Honor GOD, Country and Corps

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    I love little saws. Why use anything bigger than necessary? I've got a 170 chassis swapped up to Chi-com 180 engine and carb. Bend open the muffler lovers and they breath much better. Mine runs like a Beaver on crack but it's always temperamental starting, hard to hear that first pop and easy to flood if you persist on full choke.

    The best modification on this saw is to swap out the chain tensioner from the OEM front screw to a side adjustment.

    Is there a metal side plate cover available?
     
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  14. Jasonrkba

    Jasonrkba ArboristSite Guru

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    I have two of them and use them all the time for Clean up. I changed my carbs out and they run a lot better. It usually takes 3-5 pulls to start. One of them has an aftermarket piston and cylinder, I can't tell a difference between the two.
     
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  15. Nathan Graff

    Nathan Graff ArboristSite Member

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    I'm interested in the side tensioner swap. I require to know more... haha

    On the other hand, it's still oiling a lot more than it needs to. Is there an adjustable oiler available that will fit?
     
  16. Jasonrkba

    Jasonrkba ArboristSite Guru

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    Is it leaking out the bottom or just slinging oil off the bar?
     
  17. Nathan Graff

    Nathan Graff ArboristSite Member

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    It was leaking out the bottom, but I replaced the line. Now, it's slinging a lot of oil off the bar. Takes about 5 seconds to get a very solid line in something from it.
     
  18. Jasonrkba

    Jasonrkba ArboristSite Guru

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    Its non adjustable. I had the opposite problem with mine. Regular bar oil was to thick so I had to change to 30wt.
     
  19. Jasonrkba

    Jasonrkba ArboristSite Guru

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    Sounds like yours may be ok.
     
  20. anlrolfe

    anlrolfe Honor GOD, Country and Corps

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    If I recall correctly, the 250 tensioner swaps out

    Untitled1.jpg
     

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