Need ideas on FS 111RX poor running engine

[MagnumMike]

Hi guys! I have a one year old trimmer that has problems producing full power. Since new, the machine starts fine but only seems to reach half throttle, regardless of how much I squeeze the trigger. The machine has less than 10 hours on it (I keep track). I only use non ethanol fuel along with Stihl HP Ultra 2 stroke oil. From idle to half throttle is normal. After that it won't rev up any higher. Recently during a 90* day in upstate NY, I could not keep it running. I needed to continually "play" with the throttle just to prevent it from stalling. Releasing the throttle caused it to die immediately. It continued to start on first pull, but would not stay running without playing with the throttle. Seemed like it was starving for fuel. Before storing last winter, I ran Stabil 360 through engine and then drained fuel tank. Dealer suggested rebuilding the carb with a new kit. That doesn't make sense to me, given it is 11 months old with less that 10 hours on the engine. Any thoughts on this issue are greatly appreciated!!

Thanks in advance!

Mike

 

[mechanic mark]

Absolutely, I use 93 octane gasoline with fuel additive Star Tron in 5 gal. gas can per instructions on bottle in all outdoor power equipment.

Fuel - John Deere Fuel Treatment

https://www.google.com/search?q=john+deere+fuel+treatment&oq=john+deere+fuel+treatment&aqs=chrome..69i57j0j69i60l2j69i61.19212j0j4&sourceid=chrome&ie=UTF-8

www.lawnmowerforum.com

https://www.stihlusa.com/WebContent/CMSFileLibrary/InstructionManuals/STIHL-FS-111-RX-Owners-Instruction-Manual.pdf

Read page 18 concerning ethanol & unleaded, paragraph 4 is why I choose to use 93 octane gasoline.

STAR TRON - Google Search

 

[Fish]

Taqke a look at the screen in the muffler. It could be carboned up too much, and giving you problems.
Like a potato in your tailpipe...

 

[Fish]

If it is,
look at your air filter.

 

[slomo]

With only 10 hours on a new engine, you might have your fuel mix messed up. If you remove the muffler and the window (spark arrestor) screen is plugged with carbon, your mix is waaay off. I would take it back to the dealer and make them fix it under warranty. Course they are going to tell you that you used the wrong octane and too much oil, blaming you. Then politely ask them when will it be fixed.

Make sure you SHAKE/SWIRL your fuel can every time before filling. I've seen boats where guys dump oil in the tank and it never mixes. One boat was half full of oil sitting on the bottom of the tank. Guy was complaining about fuel range LOL.

Make sure the throttle trigger is giving you full throttle AT the carb. Throttle cable routing might need looked at.

Sure sounds like a plugged exhaust.

When you put the 360 in, did you shake the can?

slomo

 

[Fish]

Then again, I missed the "since new", and "only 10 hours" parts.
Likely the gas is bad by now, and should be replaced.
But you must realize that these four stroke trimmers run a whole lot slower, but have much more "grunt".

 

[MagnumMike]

Then again, I missed the "since new", and "only 10 hours" parts.
Likely the gas is bad by now, and should be replaced.
But you must realize that these four stroke trimmers run a whole lot slower, but have much more "grunt".

 

[MagnumMike]

Hi guys! I have a one year old trimmer that has problems producing full power. Since new, the machine starts fine but only seems to reach half throttle, regardless of how much I squeeze the trigger. The machine has less than 10 hours on it (I keep track). I only use non ethanol fuel along with Stihl HP Ultra 2 stroke oil. From idle to half throttle is normal. After that it won't rev up any higher. Recently during a 90* day in upstate NY, I could not keep it running. I needed to continually "play" with the throttle just to prevent it from stalling. Releasing the throttle caused it to die immediately. It continued to start on first pull, but would not stay running without playing with the throttle. Seemed like it was starving for fuel. Before storing last winter, I ran Stabil 360 through engine and then drained fuel tank. Dealer suggested rebuilding the carb with a new kit. That doesn't make sense to me, given it is 11 months old with less that 10 hours on the engine. Any thoughts on this issue are greatly appreciated!!

Thanks in advance!

Mike

With only 10 hours on a new engine, you might have your fuel mix messed up. If you remove the muffler and the window (spark arrestor) screen is plugged with carbon, your mix is waaay off. I would take it back to the dealer and make them fix it under warranty. Course they are going to tell you that you used the wrong octane and too much oil, blaming you. Then politely ask them when will it be fixed.

Make sure you SHAKE/SWIRL your fuel can every time before filling. I've seen boats where guys dump oil in the tank and it never mixes. One boat was half full of oil sitting on the bottom of the tank. Guy was complaining about fuel range LOL.

Make sure the throttle trigger is giving you full throttle AT the carb. Throttle cable routing might need looked at.

Sure sounds like a plugged exhaust.

When you put the 360 in, did you shake the can?

slomo

 

[MagnumMike]

Thanks for the quick reply! To clarify, I'm using Sunoco 90 Non-Ethanol with the Stihl Oil. The mix is fine as I'm using the same fuel/oil mix in my leaf blower and chain saw with no issues. The lack of power issue start with the very first tank of fuel. I did not keep any fuel in the machine over the winter. After emptying the tank, I ran the engine till it quit. I will check the spark arrestor, but can they clog up after such a short period of time? Previously I had a John Deere trimmer that the arrestor plugged up after 10+ years of use.

 

[Fish]

Can you put up a video of it running?