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Stihl FS75 won't start

Discussion in 'Mechanic and Repair' started by jballe01, Jul 5, 2008.

  1. jballe01

    jballe01 LawnSite Member
    Posts: 3

    I got a Stihl FS75 at auction and am attempting to fix it to give away to a friend. Unfortunately, it's not starting. I'm starting with the switch on, choked and primed. I have cleaned the carb and cylinder, put new gas in and have seen a spark from the plug detached from the cylinder when I pull the crank. The cylinder does appear to be getting gas, but there isn't any noise like its starting to catch the spark and turn over. The only other thing it does out of the ordinary is the trimmer head rotates when I pull the crank.

    What should I try next? I have a spare cylinder and carb that I could use to swap what's on it now.

  2. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Posts: 1,164

    Need to check compression anything under 100lbs is going to be suspect. Need to check spark with an in-line tester since checking spark with the plug out of the cylinder requires less resistance to fire the plug then with it in. Inspect the seals on the crank both front and rear and not a bad idea to look for scoring or vertical scratches on the intake and exhaust side of the piston.
  3. jballe01

    jballe01 LawnSite Member
    Posts: 3

    Thanks, I will try both (compression and in-line) and let you know the outcome.
  4. mowermankevin

    mowermankevin LawnSite Senior Member
    Posts: 270

    jballe, yes to all the things MowerMedic said, also if the shaft is turning when the recoil rope is pulled, the clutch springs are out, this requires pulling the front off the trimmer after disconnecting the throttle cable/kill wire that is tucked in the black plastic that goes into the orange engine top cover. See if it will start and run first, cause no point in fixing the clutch if it won't run, might end up just being a parts machine if theres no compression.

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