Stihl FS-75 problem

Tag1260June 2, 2013

I have a Stihl FS-75 line trimmer and it runs great at high speed and starts pretty easy. The problem is that it won't idle down. I can't get it to idle low enough to get the head to quit spinning at a fairly high speed. There are no high and low needles to adjust on the carburetor. Any ideas?
Thanks
Tag

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loger_gw

There should be a screw related to the linkage vs carb if you look close. I feel something is miss aligned (if you look close) if this has not always been a problem.

    Bookmark   June 2, 2013 at 10:20PM
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Tag1260

Thanks for the reply. I guess after reading I wasn't entirely clear. I know the screw you are talking about. I can adjust that lower, but the engine stops running when I get too low, before I can get it idling at a low RPM. There's another screw that looks like some sort of needle adjustment but it's square on the end. It also doesn't do anything until it's completely removed.

    Bookmark   June 2, 2013 at 11:29PM
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loger_gw

Has this always been a problem vs just starting? Some new carbs have no adjustments and some have limits. I have remed plastics limits and sollve problems.

    Bookmark   June 2, 2013 at 11:44PM
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Tag1260

Started last fall but put it off until now.
Thanks

    Bookmark   June 3, 2013 at 12:08AM
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frontiercc(MD Zone 6)

How old is the trimmer? My Stihl needs a carb rebuild every 3 years or so. The new gas kills the flexible parts in the carbs.

A carb rebuild kit is only a few bucks at the Stihl dealer and it is a fairly simple process with hand tools and Utube vids. If your trimmer is more than 3 years old, it might be just as effective to pull the carb and rebuild it completely.

Get a new filter/ clunker for the tank while you're at it so it can draw plenty of clean fuel.

    Bookmark   June 3, 2013 at 9:27AM
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loger_gw

Have you used Stabil or any additives for the corn gas per tank used (if you use corn gas)? I have treated 2 gals per purchase since the start of corn gas and have not seen one related problem yet.

A good inspection for deteriorations (fuel lines, diaphragms) and cleaning (screens, etc) would be a good idea with these symptoms (as mentioned).

Are RPM issues usually a sucking air matter or what?

Good Luck!

    Bookmark   June 3, 2013 at 11:19AM
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