Average Compression Reading

Discussion in 'Mechanic and Repair' started by Butch1957, Feb 13, 2008.

  1. Butch1957

    Butch1957 LawnSite Member
    Messages: 106

    What would be an average compression reading on a Used chain saw ( or any other two cycle lawn equipment ) ? I am sure it would depend on the brand but on an average what would be the Cut Off Point Reading when one determines it is not worth fixing.

    Any suggestions would greatly be appreciated.

  2. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Messages: 1,164

    A new unit will easily pull 120lbs of compression and anything down to around 100psi is acceptable. Once they get below 100lbs or closer to 90lbs they will sometimes still run but usually not well. Anything 90lbs or less is DONE!

    On a side note, I have pulled compression on units over 100lbs and they still would not run because of scoring to the piston and cylinder wall below the rings so always a good idea to check the intake and exhaust side of the cylinder to be safe.
  3. shop22

    shop22 LawnSite Member
    Messages: 134

    Same here, check the piston and if all looks ok you should get about 100lbs without too much trouble.
  4. Butch1957

    Butch1957 LawnSite Member
    Messages: 106

    Thanks for the input; Shop & MowerMedic.

    I appreciate in information.
  5. randy448

    randy448 LawnSite Member
    Messages: 39

    Quick test I was told years ago,pick it up by starter pull handle. If rope unspools bad news. Dont know how great big bar affects it but it is pretty good and fast check.:usflag:

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