Stihl FS-45 Weedwhacker Running Issues

[Astro_Guy]

I have a Stihl FS-45 weedwhacker, probably five or more years old. I mixed pump gas at 50:1 for its first season but have run ethanol free Tru-Fuel 50:1 since then.

The machine sat idle for all of May in need of a new cutting head. The new cutting head was installed on Memorial Day (31 May) and I tried to fire it up. There were 2-3 ounces at most of fresh fuel in the tank. It would start and then stall out immediately as if only the primer charge was getting there. This went on for a while, so I added more fresh fuel but no joy. I forgot to mention that the exhaust screen was clean.

Next I added a little bit of Sea Foam. Maybe a half an ounce? In any event, the machine continued to start but would stall out on any touch of the throttle. It would run 3-4 seconds at this point. I added more Seafoam - maybe two ounces at most. I let it sit for three hours and tried again. At this point it would run continuously at full throttle but any slight leaning of the motor or touch of the throttle would cause it to stall instantly.

Tonight I went out an gave it another go. That's five days of soak time for the Seafoam. It ran normally with full throttle response and no stalling. This isn't a product endorsement, but Seafoam does appear to have solved my problem.

 

[xgmad]

Seafoam does work on small engines, especially good for 2 strokes.

I just use paint thinner, NO ACETONE.

One time i ran my cheap craftsman with acetone and oil, haha!
Everything died in it.

 

[Markopolo]

Seafoam is great stuff, however, I would bet that your diaphragm in the carb is starting to go, easy enough to replace (around 8$ for the part and 30ish minutes of your time if you're a novice)

the main reason it worked again is that the seafoam had soaked the diaphragm and made it soft again.

or you really had some crap in there and seafoam cleared it out, either way, glad that stihl is still working strong for ya!

 

[Warstud]

I go thru that same scenario every couple of years with my weedwhacker and all I do is run some Techron with the choke on and eventually it starts running normal again.

 

[tig1]

I decided to only use Stihl fuel in my Stihl weed wacker. It has 93 oct., ( no ethanol ), syn oil, and fuel stabilizer. It is expensive but I don't use all that much fuel, and their fuel has performed flawlessly in my three year old machine. About $8 a qt.

 

[JHZR2]

I decided to only use Stihl fuel in my Stihl weed wacker. It has 93 oct., ( no ethanol ), syn oil, and fuel stabilizer. It is expensive but I don't use all that much fuel, and their fuel has performed flawlessly in my three year old machine. About $8 a qt.

Agree. Ive had a stihl stick edger I use just a few times per year, very little gas. Starts and runs perfect Every time.

 

[Warstud]

I decided to only use Stihl fuel in my Stihl weed wacker. It has 93 oct.

There really is no difference between Stihl Motomix and Trufuel. All the specs are the same. Trufuel is a couple bucks cheaper tho.

 

[Skol8480]

I'm a big believer in using Sea Foam. I add it to my gas cans for all of my OPE and I've never had any carb issues in 16 years of home ownership with the exception of one awful, piece of junk, Chinese MTD Troy Bilt 4 cycle weedeater. The only fix for that hunk of junk was trashing it and buying a Stihl.

 

[Astro_Guy]

I'm a big believer in using Sea Foam. I add it to my gas cans for all of my OPE and I've never had any carb issues in 16 years of home ownership with the exception of one awful, piece of junk, Chinese MTD Troy Bilt 4 cycle weedeater. The only fix for that hunk of junk was trashing it and buying a Stihl.

I cannot recall when or why I bought the Sea Foam. All I can say is that I had some, tried it on what seemed to be a fuel issue, and the problem went way. I run ethanol free gas in all of my OPE and generally don't treat it with anything before the end of the season. End of season treatment has been Sta-Bil, never Sea Foam.

 

[ARB1977]

My Sthil attachment engine has no issues in the 8 years I’ve owned it. Started off with their moto mix for 5 years. Then my own ethanol free fuel I made with Amsoil Saber 80-90:1 for two years. Now I run 93 E10 with Saber at the same ratio. Last year I changed the plug and filter.

 

[Astro_Guy]

Just a quick follow up 2-1/2 weeks after the original post. The FS-45 is running as good as new now. It's running better than it did at the time of the original post, meaning faster throttle response and never bogging down under load.

 

[Warlord]

I used to use seafoam a lot with mixed results but now anytime a piece of eq is giving me issues I just drop the carb in my ultrasonic cleaner for a half hour or so. Hasn’t failed me yet!

 

[Astro_Guy]

I have a Stihl FS-45 weedwhacker, probably five or more years old. I mixed pump gas at 50:1 for its first season but have run ethanol free Tru-Fuel 50:1 since then.

The machine sat idle for all of May in need of a new cutting head. The new cutting head was installed on Memorial Day (31 May) and I tried to fire it up. There were 2-3 ounces at most of fresh fuel in the tank. It would start and then stall out immediately as if only the primer charge was getting there. This went on for a while, so I added more fresh fuel but no joy. I forgot to mention that the exhaust screen was clean.

Next I added a little bit of Sea Foam. Maybe a half an ounce? In any event, the machine continued to start but would stall out on any touch of the throttle. It would run 3-4 seconds at this point. I added more Seafoam - maybe two ounces at most. I let it sit for three hours and tried again. At this point it would run continuously at full throttle but any slight leaning of the motor or touch of the throttle would cause it to stall instantly.

Tonight I went out an gave it another go. That's five days of soak time for the Seafoam. It ran normally with full throttle response and no stalling. This isn't a product endorsement, but Seafoam does appear to have solved my problem.

Just a 2022 update on the Stihl FS-45. I mixed 2-1/2 gallons of 50:1 fuel last December using 89 Octane E0 plus Husqvarna 2-cycke oil. This was for my 2-cylce snowblower, but it didn't snow last year. I've been using that fuel in the chainsaw and leaf blower, also Stihl products. Recently the FS-45 started bogging down under load and shutting off when hot. I thought it might be the fuel, but the other two machines were running fine.

Yesterday I removed the exhaust screen. It didn't look bad, but I burned it off with a propane torch just to be sure. Wouldn't you know that that simple action put everything right? The question rolling around in my mind right now is why I've never had to touch those screens on the chainsaw or leaf blower, both of which probably have more hours. Any thoughts?

 

[jeepman3071]

Just a 2022 update on the Stihl FS-45. I mixed 2-1/2 gallons of 50:1 fuel last December using 89 Octane E0 plus Husqvarna 2-cycke oil. This was for my 2-cylce snowblower, but it didn't snow last year. I've been using that fuel in the chainsaw and leaf blower, also Stihl products. Recently the FS-45 started bogging down under load and shutting off when hot. I thought it might be the fuel, but the other two machines were running fine.

Yesterday I removed the exhaust screen. It didn't look bad, but I burned it off with a propane torch just to be sure. Wouldn't you know that that simple action put everything right? The question rolling around in my mind right now is why I've never had to touch those screens on the chainsaw or leaf blower, both of which probably have more hours. Any thoughts?

There are a lot of factors influencing why one machine would carbon up the screen and another wouldn't. The other equipment might be running a tad bit leaner, allowing it to get hotter and burn off the carbon in the screen, or they are run at wide open throttle for longer. I see a lot of weed trimmers with clogged screens, because people tend to idle them and only touch the throttle briefly while trimming.

 

[KrisZ]

The question rolling around in my mind right now is why I've never had to touch those screens on the chainsaw or leaf blower, both of which probably have more hours. Any thoughts?

Most likely it’s because chainsaws and leaf blowers are operated at WOT most of the times, trimmers are not because they kick up a lot of rocks and dirt. That’s assuming the mixture is proper for all equipment. Too much oil will clock the screen as well.

My 11 year old Echo trimmer still has the original screen that has not been cleaned. I always run it at WOT, except in few situations. Mix is 50:1 using Echo oil.