Fixed My Stihl FS45 Trimmer!-Easy Fix

[VaTom]

I have a 9 year old Stihl FS45 weed trimmer. Never had a problem with it. Use their oil-mixed properly. Yesterday it started "bogging down" and would not run at higher RPMs whenever I tried to use it. Rough idle also. Checked the air filter-OK, Put in new spark plug, still no fix. Went on line and found that the likely problem was a clogged (carbon build-up) spark arrestor screen in the muffler assembly.

Took the muffler off (could probably do this repair without taking off muffler). The spark arrestor screen is on the inside of the exhaust port (nipple looking thing where the exhaust comes out). It screws into the muffler and you can take it out with a 15 mm wrench. It was clogged with carbon buildup. Used some CLP with a wire brush and cleaned it up and blew it out with compressed air.

Bingo!-The trimmer runs like brand new. (Owners manual says to take it to a Stihl techinician to have the screen cleaned or replaced and has no instructions on how to do it.)

Easy fix and saved myself time and money.

 

[Steve912]

I fixed my gas powered trimmer, too.

Got one of the HF 80 volt models. Thing's a beast.
Finally got it to bog down, eating a tarp. No comparison
to gas, none.

 

[The Norseman]

Trimmer Hack

Great Thread. I have a Circa 90's Home-Lite plastic string grass
trimmer.

I too took out the Muffler Spark Arrestor Screen out. I tried to
clean it up, but the carbon build up was caked on bad after all
these years.

I wish I had known about this Trick many years ago. By removing
the SAS my Trimmer starts and works so much better.

Great fix.

P.S. Sometimes I could not get the Line to Bump Feed out of
the Trimmer Head smoothly, so one day after reloading the
Line I sprayed the Head down heavily with a car Interior
Protectant. The Line appears to feed out better now

 

[wetdog]

^^^^^^^ I had a Homelite from that era that I got rid of a year or 2 ago and I still have 2 string heads and 4 spools laying around. If they look like the same as yours let me know and I'll send them to you. Part numbers are DA03001A for the head and UP00145A for the spool.

 

[Minorcan]

Got a trimmer like that. Every season I take the screen out (mine just slides out) and heat it up good with a propane torch. Spray it with a bit of brake cleaner. Takes about 5-10 minutes.

 

[ColbyBruce]

My Stihl FS 55R trimmers, 029 and MS 170 chainsaws all use this in-line fuel filter inside the fuel tanks. A new filter each year makes for a better running unit too.

 

[kraynky]

I'm glad this thread got started. My FS85 was bought new in 1995, and has never been to the shop. This junky ethanol fuel has caused all sorts of fuel line problems on my small engines, but the FS85 is starting to bog down a little, even using the expensive pre-mixed fuel.

I'd forgotten all about those spark arrestors clogging up. My Lawn Boy mower used to do that now and again, and that always fixed it. I'm going to give it a try. That thing is a weed whacking beast! (when it's running right) Twenty five years is too young for a Stihl to wear out.

 

[Kinman]

The old trick was to set the screens on fire, then brush the residue off...not unlike burning out an old set of glasspacks. I've always liked Stihl's products, our building maintenance/yard crew used Stihl products exclusively. I fell in love with their new 2-stroke technology that turned their larger string trimmers into something that sounded more like a 4-stroke. I liked the equipment so much that I bought it for home use 20 years ago and am still using the stuff regularly, probably outlive me. I have a little 0145AV Stihl chainsaw that I have had for nearly 40 years that although it has sat for five years or more I bet I could go out and start that dude on three or four pulls.

 

[wheelgun28]

If you don't live in a wildfire area do you need to put the screen back in? Will it change the air-fuel mixture by taking away backpressure.

Asking for a friend...

 

[IronSkillet]

FWIW purchased the tune-up kit for my FS-45 from Amazon, was amazing how dirty that fuel filter in the tank was, works great now. Glad you got yours up and running.

 

[VaTom]

If you don't live in a wildfire area do you need to put the screen back in? Will it change the air-fuel mixture by taking away backpressure.

Asking for a friend...

From my research on line, folks said theirs ran fine without it.

VaTom

 

[Kinman]

It will probably be louder, we were discouraged from making things louder because of public complaint when operating in urban settings. I always wear hearing protection...

 

[MRB1]

The spark arrester is the first thing I remove when I do a full maintenance. The Stihl trimmer has the screen in a plug that screws into the exhaust - I just grind it off flush. The chainsaws have a screen that is removable. I discard it completely. You'd be surprised how much better they run without the obstruction - even a new screen restricts the exhaust somewhat. Also, the pre mix fuel is a lifesaver - 94 ethanol free fuel and the correct amount of oil. It is more expensive, but better for the engines. Those screens are another "safety" that you can easily do without - unless you're working in a national Forest.