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Stihl FS110rx won't run

Discussion in 'Mechanic and Repair' started by Lorge, Apr 14, 2008.

  1. Lorge

    Lorge LawnSite Member
    Messages: 35

    Havin a problem with my trimmer. Some help would be appreciated. Let me start from the beginning so diagnosis will be easy (as possible). This unit was purchased new in spring 2005. It has run like a champ, until now. I used it commercially (light) when I had my lawn business, but only use it at a homeowner's level, since spring 2006. So 1 season of light commercial, 2 as homeowner. It ran great through the end of last year, but I didn't drain the fuel or put an additive in it this winter. Reason is, it was in Dallas and I was in Waco. My dad was mowing my yard in Dallas while the house was on the market. The house sold in March of this year, so that is when I got the trimmer from sitting in the garage since October/November. So, it sat for about 5 - 6 months.

    Went to crank it up last week, and it wouldn't start. I added a little carb cleaner (Seafoam Deep Creep) to the carb from the air intake, put the air filter back on, and tried to crank. It still wouldn't start. It seemed to fire a little and put out some grey smoke when it fired. Wouldn't come close to actually running though. I then checked the plug. It was nasty. Lots of carbon build up on it. I don't think I've ever changed it. :hammerhead: I knew it needed replacing, but I wanted to get the thing running at least for now, so I sprayed some Seafoam in the spark plug opening. It fired on a few pulls and put out some grey smoke, but never actually started. It was good to see a sign of life. I gave up that day after 20 more pulls.

    I went to my dealer and bought a new plug and fuel filter. I drained the gas that was in the tank. I realized that it was actually from last fall, maybe even late summer. I put in new mixed gas. I installed the plug and fuel filter. Tried to crank, but nothing. So I went with the carb cleaner again. Sprayed some in the carb - kinda fired and put out grey smoke, but wouldn't start. I took out the plug and sprayed a liberal amount in the spark plug opening. Put the plug and wire back on. IT CRANKED and ran strong....for about 5 seconds, then died - sounded like an engine running out of gas. I pulled it a few more times, it ran a couple more times, but only for a second or 2. It seemed like it was running on the carb cleaner I sprayed, not the intended fuel. I pulled it quite a few more times, but nothing happened.

    Where do I go from here?

    It seems fuel is not getting to the engine. Should I disassemble the carb and clean it with carb cleaner? Should I get a carb rebuild kit? How difficult are these carbs to work on? I'm handy, but am a novice at engine repair.
  2. sawman65

    sawman65 LawnSite Senior Member
    Messages: 754

    sounds like you did not use the stihl mix if you did you would not have this problem. you see stihl mix has stablizer in it. any who you need to rebuild the carb or replace it. kits at the dealer go for 20 or so dollars to do it right.best and easyest thing to do is get a new carb @ 60.00 its a deal and it takes just a few minnutes to do. i know people on here will blast me for telling you this. but take it from a dealer those zama carbs dont rebuild well. the main jets are a pain and cant be replaced.
  3. Lorge

    Lorge LawnSite Member
    Messages: 35


    I've used nothing but the stihl 2 cycle oil in the orange bottle. Is that what you are calling stihl mix?

    Is it likely the carb is my only problem? Or might there be other things that need repair? I agree that $60 for a new is more cost effective than $20 for a rebuild, considering I'm not very familiar with rebuilding carbs.

    S DIAMOND LawnSite Member
    from South
    Messages: 108

    The fact that your unit runs when you "prime" it, is an indication that it seems to lack good fuel delivery. You have eliminated compression and spark because it runs for a few seconds when you goose it.

    You will need to remove and clean the carburetor. Replace the gaskets (including the carb mounting) and diaphragms. It is not super hard to do. Lay out the new pieces and replace them exactly how the old ones come out. Get a can of carburetor cleaner (with red stick) and clean all the orifices. Note: do not mess with the needle "lever" unless its way off. Take a picture with a digital camera if you don't feel comfortable about it. Otherwise, take it to someone you trust to rebuild it, and mix stabilizer with all your future fuel purchases. Good luck:)
  5. GiddyUpGo

    GiddyUpGo LawnSite Member
    from Arab,AL
    Messages: 4

    I have two KM110R combi motors. I had a similar problem after about 4 months of commercial use, and I went through the same trouble shooting steps.Sawman is right about stihl's oil.The salesman told me upfront to never add stabilizer to the mix.
    My problem was carbon buildup in the muffler. Take the muffler off and give it a try. If it runs,you can effectively clean the muffler by slapping the flat side against a brick and shaking the carbon loose through the muffler's intake hole.
    Sure beats buying a new muffler every few months.

    God Bless.
  6. Winslow Mountain Lawncare

    Winslow Mountain Lawncare LawnSite Member
    from Lyme NH
    Messages: 36

    I had a similar problem with my fs110 and also thought it was a carb problem. It turned out to be the valves were out of adjustment. They are supposed to be adjusted after 10 hrs and then every 100 after that. I run amsoil and havent had any problems....
  7. Lorge

    Lorge LawnSite Member
    Messages: 35

    Wanted to give an update on my problem. I still can't get it to start.

    I've disassembled the carburator and sprayed every possible orfice. The internals of the carb were kind of dirty.

    I checked the fuel line by removing it and blowing through it. Didn't seem to be any blockage.

    I also removed the screen on the spark arrestor, and repeatedly tapped the spark arrestor on cement. A LOT of carbon came out.

    After reassembling everything, I'm still having the same symptoms. It will fire, but only when I've sprayed carb cleaner directly in the cylinder. It really won't even fire from spraying in the carb.

    Any direction?
  8. SLR

    SLR LawnSite Gold Member
    Messages: 3,210

    My advice:
    If you allow the fuel to sit for more that 2mths, Don't Even use the mixed gas/oil in tank to even start it. My belief is if your gonna buy a high quality stihl/husky etc, keep the oil/gas mix updated regularily,as the 2stroke oil breaks down after so many sitting hours. I actually siezed my old IT495 using old 2stroke oil, sitting from the previous summer and holding it wide open on the road like the idiot i was.
  9. Breezmeister

    Breezmeister LawnSite Bronze Member
    Male, from South Jersey
    Messages: 1,784

    Compression and leak down test.....if you have the tools. Just because it will fires when you spray "fuel" into the cylinder doesn't mean that there is enough compression.
    ericg likes this.
  10. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,456

    Adjust the valve assuming the unit has valves.....I am an Echo guy but if it has valves and they are not adjusted it will not start.

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