Stihl FS55 won’t idle

Plbjr123

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Apr 8, 2020
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I have a FS55 and with all the bordem from social distancing decided to do some work on my yard equipment. Changed the carb, filters, fuel lines etc, spark plug and ignition coil. I am able to get the unit to fire up and run at full throttle but when I let off it will die. When I put a little pressure(has a little play in it)on the black curved tensioner piece that holds the throttle cable behind the carb I can get it to idle. I have also screwed in the hex head screw that is supposed to apply tension to the throttle cable. I have played with the high, low and idle screw at nauseam and can’t get it to stay running unless I am on the throttle. Please assist as my arm is tired and at wits end. Thank you!
 

Fish

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Aug 2, 2013
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With the engine not running, watch the trimmer head when you pull the starter rope, it should not turn.
 

tschwarting

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On my fs 55 stihl string trimmer, I cannot get it to idle either. My question is that when I take out the low speed adjustment screw, the engine should not run at all should it?
 

bertsmobile1

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Nov 29, 2014
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That will depend on how far out of adjustment the throttle stop and High speed jet are.
I regularly get trimmers & chainsaws in the workshop where the L jet is totally blocked & the engine is running on the H jet all the time
They will work fine like that except they are difficult to start & tend to stall when you let the trigger off quickly.
Both Zama & Walbro have nice colour diagrams of exactly how the carbs work at different speeds.
 
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