stihl backpack blower losing power

Discussion in 'Mechanic and Repair' started by ferris hilton, Oct 13, 2007.

  1. ferris hilton

    ferris hilton LawnSite Member
    Messages: 33

    stihl backpack blower, maybe 4 years old, doesn't have the power it used to. Any ideas what could be wrong?
  2. GroundEffects125

    GroundEffects125 LawnSite Senior Member
    Messages: 288

    gas filter?
  3. All_Toro_4ME

    All_Toro_4ME LawnSite Bronze Member
    Messages: 1,578

    Its tired.
  4. cpel2004

    cpel2004 LawnSite Bronze Member
    Messages: 1,415

    check your gas mix ratio clean filters etc. Hope that helps, 89 octane only
  5. Stillwater

    Stillwater LawnSite Platinum Member
    Messages: 4,889

    Yes I have several, power loss?

    #1 thing to check is the muffler, while the back pack is running loosen the bolts on the blower a little just enough to get it slightly loose if it regains its power you have a clogged muffler remove it and clean it by soaking in solvent
  6. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    In relation to eshskis - Pull the spark arrester screen out of the muffler.
  7. Stillwater

    Stillwater LawnSite Platinum Member
    Messages: 4,889

    thank you it was late last night I couldent express myself clearly I ment lossen bolts on muffler
  8. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    First off I do agree, it's probably tired, doesn't feel like working right now.
    There's troubleshooting but how many hours can you spend before it becomes feasible to simply buy a new one and keep the old one for parts? How many years does it take for one piece of equipment to pay for itself also comes to mind, if this thing has, as I suspect, paid for itself 2-3 times over, well, you know it just might be time...?

    Now then:
    2-cyclers like to soak their air filters in fuel, at least on mine I have to replace these once or twice a season, this has been done, correct?
    If that air filter hasn't been replaced in the past 30 days or so, I'd do it just for gp.
    Replace the spark plug as well, I'd do a quick compression test while you got this out (at least 100 psi but 120 is better), also at this age you might consider replacing the in-tank fuel filter, more so if this isn't done as routine maintenance.

    An hour spent here for the simple stuff.
    Beyond the simple stuff we start to run into the labor cost vs. replacement factors...

    Might want to soak them overnight in a solvent, and have two replacement bolts ready as well, since you'll want to be prepared to drill the old ones out if need be... Yes, after 3-4 years they can certainly be at least that stubborn. Hopefully a local hardware store carries something of this nature, these bolts are not cheap from the dealer, the muffler itself is far worse, maybe you have another machine laying around broken can spare them?
    btw this would be one reason I always keep broken machines for parts...

    By now you'll be 3-4 hours into it.
    The coil would also be suspect, do you have a spark STRENGTH testing tool?
    As would the carburetor, maybe soak it in carb cleaner.
    2-3 more hours.

    Ten or more labor hours plus parts and it might run, or buy a new one that does, up to you.
    Keep the old one for parts.
  9. Leaf Jockey

    Leaf Jockey LawnSite Senior Member
    Messages: 378

    Checking the air filter is a good suggestion. Also the guy has had the blower four years and probably never decarboned it or he wouldn't be asking the question. Excess carbon buildup in the exhaust port and spark arresting screen are the most common reasons for power loss. That would be a good place to start because it is a common problem, costs nothing and won't take very long to do.
    If a person wants to do all the things listed I would suggest doing one at time. That way you would learn which efforts gained the desired results. This way a person learns where to look when this happens again.

  10. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    I'm not disagreeing, but the last time I took an old muffler off the rust had coated everything so severely I literally had to drill the screws / bolts out of there... Sometimes the tool fits, other times vise grips work, still sometimes it breaks the head off, so some will come off relatively easy, others won't.

    But it is a trick to check into, I've done it before and you are correct, if the exhaust PORT is clogged, you will lose power.

    Interestingly enough, this is how I found out a Stihl fs-85 and an Echo srm-260s muffler are interchangeable :laugh:
    They are different in size, but the fit is perfect, port, bolts, exact.
    Hence why I preach never throw the old machine away.

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