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ARGH! Got my first bad Stihl.

Discussion in 'Lawn Mowing' started by swingset, Aug 6, 2007.

  1. swingset

    swingset LawnSite Member
    Messages: 231

    Decided to buy a 3rd FS90, I have a 90 & a 90R with the bikehandles that I use for the heavy/brushcutting but it makes a lousy backup to the lite yard work and the regular 90 I have is getting long in the tooth. The new 90R is a 4-mix and I really like it so I took advantage of my dealer's sale and nabbed a new 90.

    He put half a tank in and started it up at the shop before I left and it seemed to run fine, but when I got home later that day I had a heck of a time with it. It was sluggish to start, and died or bogged down when trying to go full throttle. Idled ok, for a while, but it didn't take off good if you blipped the throttle, and wouldn't run wide open at all, just kind of sputtered at half-power.

    I double checked everything, tried again but the same result. The gas is definitely good, it's running fine in the other trimmers so I was sure it's not that. Then, I noticed that if I dipped the trimmer forward, almost straight up and down, it took off and ran wide open. Dip it back down again, let it idle for a minute and it acts up again.

    I think I've got an air leak in the fuel line or the pickup.

    Oh well, I figure after 8 perfect Stihl buys it goes to figure I get one with some bugs. I'll let the shop handle this one as it's only a couple days old but I'm betting there's a leak somewhere.

    I was kind of ticked at first, because earlier at the other dealer in town I tried out their new Kawi trimmers, a KGT27 and was really impressed with the quality and power in such a light trimmer, almost bought one but decided at the last minute I didn't want 2 different brands. Oh well, hopefully it gets worked out....I know Stihl still makes a good unit.
  2. topsites

    topsites LawnSite Fanatic
    Messages: 21,653

    First I'd like to ask you kindly, IF you figure out the fix to that would you post it?
    Because my fs-100 does that crap except it takes off fine when the head is above the motor, then when I dip it down to start trimming it dies... Not even straight down, just a slight angle down and brrrrttt.t..t..t, once I tilt the front back in the air vrooooooom!

    Yeah, I'd take it back, it's probably an easy fix, since mine's 2 years old I can't take it back for this problem, but I'd like to know...

    In the meantime, the only thing I found that works is WOT it real good for about 2 minutes at the sweet 'dipped' spot, then it's usually ok after that, sometimes I have to do this 2-3 times before it acts right, pita waste of time and fuel lol.

    Yup, 4-mix, ran great up until this year, not a problem all of last.
    Yes, I've replaced the air filter, the plug, and adjusted the screws to specs...
  3. swingset

    swingset LawnSite Member
    Messages: 231

    Sure sounds like yours has the same problem. It almost has to be fuel...what else would be affected by the attitude of the trimmer/motor?

    On mine, I thought it was a leak up near the top of the tank in the hose. If you think about it, at one pitch it's sucking air, but when you tip it the gas sloshes over and covers up the leak and then it's good.

    Dunno, but I'll post updates as I find them. I sure like my 90R and it runs strong so hopefully it's just something stupid. I could probably tear into it and find it but a 2 day old trimmer? That's the shop's problem it should be perfect.
  4. swingset

    swingset LawnSite Member
    Messages: 231

    A quick update:

    Took the trimmer back to the dealer, and he fiddled with it for a while with me and said he'd have to tear into it and double-check the fuel system and replace the fuel line and pickup to make sure it was good.

    He did tell me they had received 2 FS90R's like mine that did the same thing in the last year or so (out of 50 or so) and both had some sort of problem with the carb. He said they were out of spec or had manufacturing defects that he couldn't work out and went back to Stihl. He said if he couldn't fix it by tomorrow, he'd give me a brand new one but I told him I was really wanting to know the issue for my own 2 cents.

    I'll let ya know what I find out.
  5. All_Toro_4ME

    All_Toro_4ME LawnSite Bronze Member
    Messages: 1,578

    I'm interested in knowing as well. I have the same model stihl trimmer you have and am having the same problems. :dizzy:
  6. DuraCutter

    DuraCutter LawnSite Senior Member
    Messages: 806

    Most of the Stihls have spark arresters at the muffler exit. Those will clog up and give you all the symptoms you talked about.

    It's an easy fix, usually you have a nut there and you can take it out and clean the mesh or plain remove it if you want. With Stihls this should be one of the first things you check out.

  7. swingset

    swingset LawnSite Member
    Messages: 231

    The trimmer had about 2 minutes on it when it started acting up. I actually did check the arrestor to see if it was somehow blocked from the factory but there's no way it was clogged the thing was brand new.

    It's a popular thing to look for, but honestly I've run my Stihls with the arrestors in place for years and never clogged one up. I guess environmental factors, fuel type, oil, etc play into the emissions and carbon build up but it's a non-issue on my equipment (or has been).
  8. DuraCutter

    DuraCutter LawnSite Senior Member
    Messages: 806

    My bad. I didn't read closely enough to notice you only had the machine for less than a day and it was acting up.

    Let us know what happens in the end.

  9. S man

    S man LawnSite Gold Member
    Messages: 3,562

    I've had a km110 unit and never had a prob with it. I wonder why the fs90 is different?
  10. justanotherlawnguy

    justanotherlawnguy LawnSite Bronze Member
    Messages: 1,282

    My fs90 that I bought last year is the biggest POS. It is about to go on backup duty as soon as I get another Echo 260 in the next week or so...

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