Sthil FS86

ceezaahJune 27, 2010

I have a Stihl FS86 string trimmer. It's given me great service for many years, but now I can't get it to idle.

The carburetor has just been rebuilt and the machine will run with plenty of power but as soon as I release the trigger it will stall.

I tried to set the screw that adjusts the idle speed, but it still will not idle. It stalls as soon as the gas is released.

Is there another setting that I don't know about?


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Can't believe the number of Trimmer Issues lol Must be the Season . Sounds like you require tuning . If Dealer rebuilt the carb this should have been included . I'll assume you did the rebuild yourself (correctly) . 1st set the low speed jet up . 1-1/4 turns out from closed . Play with the setting 1/4 turn in or out until you can rev up the trimmer without hesitation . let the trimmer warm up , then ensure that the high speed jet has not been affected . Start at the same setting as the low speed jet adjustment and achieve a setting between just below max rpm @ WOT and just above the blubbering stage (4 cycleing) sound. Having done this go back to the idle adjustment and set to your idle likeing , I normally set it a little high once warm to ensure proper idle during warm up off choke setting . Hope this Helps .
P.S. Ensure fuel tank is full and air filter is clean along with the fuel filter prior to carb tuning . Fuel Conditioner (cleaner) and stabil usage during preseason start up prolonged storage is always advisable !

    Bookmark   June 27, 2010 at 12:30PM
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Sounded almost like my Honda trimmer. Those days the dealer replace a new carb....NOT UNDER WARRANTY!!! and the new carb stall at idle after 10 minutes using. I kept bring back to the shop and they cannot fix it. I finally gave up, open the old carb, clean and unblock the jet and put it on the trimmer and worked since. That particular have NO adjustment, so not much can be done in turn of adjusting.

If you try EWALK's instruction and still don't work, then I have a question for you:

When you overhalt the carb, after cleaning, did you use compressed air to blow through all the small opening and parts to dry out everything? I used a compressed air can that I bought in computer store. It is perfect for this small parts. I think it is important to use compressed air in this process.

    Bookmark   June 27, 2010 at 7:17PM
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I was given a Stihl FS56 trimmer with the curved shaft that had not been used for about 5 years or more, I put new gas in it and it fired right up. The problem is with the head, it's not tuning. It seems to want to turn, but something is stopping it. I am assuming that there are bearings in the drive shaft that are frozen. If that is the case how do I go about repairing the trimmer.

    Bookmark   July 5, 2010 at 2:53PM
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Have a FS86 , great straight shaft machine..bought it new years ago, has been running great, now tried to start, almost started on first pull,now nothing.. changed plug, gas is fresh, great spark,seems like too much gas in cylinder when plug removed, bottomed out carb H and L speed jets, backed them out 1.5 turns , nothing good going on , any ideas?

    Bookmark   May 23, 2011 at 12:19AM
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