Stihl f5 46 full throttle issue

[Anthony Wendover 124]

I am working on my Stihl F5 46 trying to fix an issue.. Anytime I go to full throttle it shuts off.. But if I go full with full choke it will run. Now I have taken carb off and all looks to be excellent! The throttle cable looks good and I am stumped on what to do to correct this problem. Does anyone have any idea?

Thank you

[TT-(Moderator) 1,127]

I'm guessing you mean FS-46 string trimmer, right?

Have you ever replaced the in-tank fuel filter?

[W9JAB 156]

:drool: I have had problems like this befor your runnig lean, but why? air filter? fuel line clogged? dirt in carb? somethig is starving it for gas that why it will run choaked. :omg:

[Anthony Wendover 124]

I'm guessing you mean FS-46 string trimmer, right?

Have you ever replaced the in-tank fuel filter?

yes that is correct

I have not replaced the fuel filter.. I didn't even think of that.. I focused mainly on exhaust/carb/throttle cable.. The carb looks brilliant so it cant be that.. I'm confused as everything checks out..

[TT-(Moderator) 1,127]

That's where I would look next.

(Sounds like you already cleaned the muffler, correct?)

[Anthony Wendover 124]

I took the exhaust off of the unit but i couldnt figure out where the spark arrestor

screen was so i could heat it up let it cool and scrape it down..

[TT-(Moderator) 1,127]

We don't have any Stihl trimmers that small where I work (one FS-85 bike handle and two FS-90's) but they should be similar.

Is there a hex shaped "nut" at the muffler outlet on your machine? It should unscrew like a conventional bolt and you'll find the spark arrestor screen attached to the back side of that nut.

I spray ours with Berkebile 2+2 Gum Cutter until the screen is clean and use a brass bristled wire brush when needed. I also start the machine with the arrestor removed and run it for a few minutes at WOT so all of the carbon blows out of the muffler.

[Mike 6]

Did you look at the screen in the carb, where the gas go in?

[Anthony Wendover 124]

there is the muffler.. I see the bolt you are talking about.. Ill try to get that unscrewed and cleaned out.. Thanks for your help thus far!

[TT-(Moderator) 1,127]

Don't be afraid to start it and run it for a short time with the muffler removed.

That will help determine if a blockage in the exhaust is causing the problem.

If you still experience fuel starvation problems, it might be time for a new pump diaphragm in the carburetor along with a new fuel line and filter.

[whchris 5]

one of my stihl kombi motors was doing this there was a pin hole in the fuel line causing it to loose vacuum when reved up