Fuel line and filter, how hard?

[Sean McGillicuddy]

Have a Stihl FS81 string trimmer
How hard is it to replace the fuel line and filter?
What part # and any tricks would help.
Will not run steady up for a while then bog when slow back to running speed.
Am I on the right track?

 

[MasterMech]

Should be a pretty simple affair. If the line is just hose routed through a grommet or a hole in the tank then you just need a short length of Tygon tubing and a new filter. 5 minute job. If it's a moulded line that has the supply and return lines in one piece, then you need to get the new line from a Stihl dealer along with the new filter. Also an easy, quick replacement.

 

[clemsonfor]

Yep easy replacement just as he described, but my guess is that you have a carb issue. the filters almost never get clooged if your half concious about how you refuel. Meaning that you wipe the caked up dirt or grass from it before you open it so dirt does not just pour in, or you just dont allow dirt in there.

My guess is that you have a carb problem like plugged jets, worn diaphram, or you have an air leak causing you to suck air somewhere. Could still posibly be a bad fuel line though. While your at it replace all the fuel lines, which is just a good idea anyway and you will have access to them all when you take the shrouds off to get to the carb to replace the main line anyhow.

 

[Jags]

Could still posibly be a bad fuel line though.

Yep - a cracked fuel line can cause weird stuff to happen...and those tiny carbs - man they are picky. One spec of anything in the wrong spot and its pull down time. If you do end up pulling the carb down, make sure you have a nice clean place to work on it.

 

[clemsonfor]

Yea jags thats what i meant i just did not say it i guess. Was assuming that he knew what i was talking about. But yea could be a crack a pinhole where it rubs something. Crack can be in the tank or out of the tank. In the tank it will run fine if a crack is below the fuel line, like when full but then suck air and run lean when the fuel level drops and the crack is exposed to air.

 

[TreePointer]

Not too difficult. Lots of good vids available:

 

[WES999]

Good idea to change the diaphragms in the carb too. My Stihl trimmer would not run at all, the diaphragms were hard as a rock. Changed them and it runs great now.
I have also seen the fuel line become restricted where it passes through the rubber grommet in the tank.

 

[Sean McGillicuddy]

Fuel filter was fine ,and what a diff a new fuel line makes!
Yup fuel line!

 

[TreePointer]

Good fix, sean!