low compression ?

Discussion in 'Mechanic and Repair' started by vomeisentor, Oct 22, 2009.

  1. vomeisentor

    vomeisentor LawnSite Member
    Posts: 23

    What does that mean when the trimmer has LOW COMPRESSION 80 PSI?

    What caused this?
    When do you have to check for it and how often?
    What do you have to do to fix it?
    What is normal ? PSI for a trimmer (STIHL fs85R ?:weightlifter:
  2. madmower

    madmower LawnSite Member
    Posts: 43

    110 psi on my one low compression can be rings cylinder but at 80 psi it should still sputter and try to start drip a small amount of 2 stroke oil in the plug hole then retest the commpression if it gos up then you need new rings

    hope this helps

  3. pugs

    pugs LawnSite Gold Member
    Posts: 3,022

    We dont mess with 2 cycles with less than 100psi. Normal for your machine would probably be in the 130-150 range or higher.

    Proper fix would be a rebuild...new piston/cylinder.

    Pull your muffler off and look inside. You will probably see alot of lines in the piston and cylinder going up/down.
  4. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,206

    Try rings first......$10 versus a big load of money for a head.

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