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Stihl hs 45 problems

Discussion in 'Mechanic and Repair' started by ljhanson12345, Mar 14, 2009.

  1. ljhanson12345

    ljhanson12345 LawnSite Member
    Messages: 64

    hey guys i was wondering if any of you could help me out with my hedge trimmer. first of all its the Stihl hs 45. ive only had it for maybe three years with little use. I took it out the other day and it had problems running at full speed. It seemed like there wasn't enough fuel coming in so it would just die if i kept it running a full speed. Running at half speed it did great, no problems what so ever.

    Im thinking its a carb. issue. ive only used it maybe 15 times though. Do you see anything else that could cause this problem.
  2. Roger

    Roger LawnSite Fanatic
    Messages: 5,943

    If it has been used so sparingly, and you have kept fuel in the tank and carb, then probably the fuel mix has hardened up in the carb jets and channels. Did you always drain it of fuel entirely before leaving it idle for long periods? If not, then the fuel lines, carb, etc, probably are partially clogged, thus impeding the flow of fuel to allow it to run full speed. Suggestion: It is time for a good cleaning!
  3. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    Uhm, first thing I would do is replace that little square black-and-grey foam air filter.
  4. LawnBoydude

    LawnBoydude LawnSite Member
    Messages: 2

    Based up on your description, I would clean the carb and replace the diaphragms. It sounds like the diaphragms are stiff and no longer pumping enough fuel to keep the engine running at wide open throttle. You will also want to check the fuel lines, fuel filter, and the air filter too.

  5. ABeautifulCutAboveInc.

    ABeautifulCutAboveInc. LawnSite Member
    Messages: 118

    I have the HL 45 hedgers. I had almost 3 years of commeercial use out of them and had similar problems. I broke down the carb and soaked it in carb cleaner, rebuilt the carb, replaced plug and fuel filter. I adjusted the carb and it runs fiine now. The rebuild kit was kinda expensive, but beats buying a new carb.
  6. RonAyersMotorsports

    RonAyersMotorsports LawnSite Senior Member
    Messages: 854

    FIRST please do this before you do something that you don't have to. Remove the exhaust screen in the muffler. More than likely it has become clogged and not allowing unit to exhaust preventing you from getting full RPMS. And be sure to replace any old fuel with new fuel prior to any mechanic work.

  7. ljhanson12345

    ljhanson12345 LawnSite Member
    Messages: 64

    thanks for all the help guys
  8. Partsangel

    Partsangel LawnSite Member
    Messages: 80

    These guys have given you some really good advice, that fact that the engine is running says that your fuel pump diapham and metering diaphram are working. I would follow these two steps.

    If your carb has adjustments, you would open counter clockwise the H or high speed adjustment about a 1/4 turn and then test. If it dosnt make any difference then one more 1/4 turn ccw. If that dosnt solve the problem check and clean your tank filter. if you have done all these things and it still wont rev-up then you need to rebuild your intire fuel system or take it to a shop that can do it. of course its Spring and the local shops are filling-up with repairs so I hope the first two suggestions work.

    good luck and thanks for posting on lawnsite

  9. 4.3mudder

    4.3mudder LawnSite Silver Member
    Messages: 2,227

    Exactly. I would do this first, has not happened on my hs45, but has happend on my 250 trimmer. QUick and easy to look.
  10. carriedrewdog

    carriedrewdog LawnSite Member
    Messages: 68

    Check the muffler screen first. Before you tear into a carb you may get lucky with a little Seafoam. Worth a try.

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