Stihl line trimmer FS46 Runs good at full throtle

not normal

Check the throttle cable, sometimes they get frayed and damaged at the carb end and can stick on.

needs a rebuild and new gas lines

Start with adjusting the high and low side adjustment out 1 full turn, then adjust the idle.

Hi

Stihl recommend 0.020 (20 thousands of an inch) or 0.5 mm. Incidentally the plug gap is independent of the plug make.

Regards
Jacko from down under

rebuild carb

Please explain your problem and resubmit

http://www.mediafire.com/download/0sdchm7cd8rb2d4

Remove orange sheild,remove single screw holding head in shaft then grab head with pliers and twist side to side until complete head is free.You should then be able to grab part of shaft.On power head loosen screws {about one turn each} that hold two white case halves near trigger,I think there are four,then there is a single torx screw on the bottom of lower case half in the middle that must be taken out to allow tube to be removed.Romove flexshaft from top.Check 4 plastic burnt to flexshaft,if there is you must replace tube liner as well,usally around bent part of tube the liner will go bad.

My nephew had a problem with his Stihl FS55R trimmer, sez it would run on high for a few then quit. Sez it restarts easy and runs on idle with no problem. I pulled carb & found fuel screen full of fine contaminant. This is the screen you see when you drop the bottom pan of the carb. (single screw does it). Reassembled and the trimmer runs on high speed w/o problems. If your primer bulb doesn't pop right back up when you punch it down, it means that the fuel can't get past that screen....