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Sthil losing power.

Discussion in 'Mechanic and Repair' started by RyGuyusMaximus, Jan 4, 2008.

  1. RyGuyusMaximus

    RyGuyusMaximus LawnSite Member
    Messages: 88

    My Stihl backback is three seasons old now and its never been overhauled. I only use it for my home but this season in particular ive noticed that the engines power output is down. (its reving lower at max) So I was wondering if its a carb issue that requires adjustment and if so whats the best way to go about adjusting it?

    Thanx in advance for your help...
  2. Two Seasons

    Two Seasons LawnSite Senior Member
    Messages: 791

    I don't know what two-cycle oil you mix, but our Stihl distributor here recommends the Stihl HP Ultra, which I now use after using the Stihl regular two-cycle oil last year.

    I'd take the spark arrestor screen out of the end of the muffler, clean it in solvent, and that should help restore some power. You may need a new fuel filter as well---it's located in the fuel tank. Your dealer can change it in five minutes. Pretty cheap item.
  3. RyGuyusMaximus

    RyGuyusMaximus LawnSite Member
    Messages: 88

    Ok thanks!
  4. LawnTamer

    LawnTamer LawnSite Gold Member
    Messages: 3,986

    Yes, before you tear into it, do basic maintenance.
    1. Change air filter
    2. Change fuel filter
    3. Change plug
    4. Clean/remove spark arrester
    5. clean exhaust port
    6. If you've ever let it sit with fuel for long periods, clean the carb. and change the fuel.

    As was said above, a dealer could do all this, but none of it should be too hard.
  5. RyGuyusMaximus

    RyGuyusMaximus LawnSite Member
    Messages: 88

    Yeah Id like to learn how to do all of this myself. Do you think that all of that maintence info is in the owners manual? lol im serious...
  6. LawnTamer

    LawnTamer LawnSite Gold Member
    Messages: 3,986

    Most of it is.
    The only hard thing there is cleaning your carb.
    Air filter and plug are easy, right?
    Fuel filter... In your gas tank there are little tubes that go in from the carb, one has a little cylinder on the end, use a piece of wire with a U-bend at the end to fish it out. the cylinder is the fuel filter, it just pulls off, and the new one goes on. While you have it out, look at the line it's attached to, if it is brittle, replace it.
    As for the spark-arrestor and exhaust port, remove the muffler, hold the machine so the exhaust port, (where air comes out and goes into the muffler) is pointing down, use a flathead to scrape out any carbon build up. The spark-arrestor is a little screen, usually attached to the muffler somewhere. sometimes there is a housing right on the muffler for it. I just remove mine, but you can also replace them. Try all that, and get new high octane fuel.
  7. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Yeh the air filter is under that plastic cover on the left side (referring to it as if you were wearing it), the cover is either black or orange in color. The spark plug is located right dead top center front.

    You use that T-handled tool they gave you when you bought it, that tool fixes everything you can fix, literally.

    The air filter is easy, just loosen the screws (I think it's 2), ease the cover off, then replace.
    The spark plug is also pretty straight forward, make sure to remove the ignition wire (that black wire) by the BOOT do NOT pull on the wire itself.
    Remember the new plug, just snug it in there, you don't want it super tight.

    The fuel filter you might need a metal rod to fish the one out of the tank, but it is common for dirt to get in the tank when refilling fuel, especially during leaf season, and you need like needle nose pliers to get the clip off, other than that it's not bad either.

    Yes it's in the manual but hands on works best.
    Before you get started go get the parts from the dealer, he might have a few tips as well, dunno.

    btw for the minimal cost increase you'll see from doing this, I always run an expensive premium fuel, 93 octane, something along the lines of Texaco / Shell / Bp Amoco / Sunoco, name brands only. Don't cost you but 5 dollars or so more a year, if that, I can't see you using more than 4-5 gallons of fuel on a blower as a homeowner, we're talking 50 cents more per gallon...?
    Because it is my opinion when running super you will have less of these problems over time.
    Now for me I run super in everything 2 cycle, trimmers and chainsaws and lawn mowers too, got tired of it.

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