Stihl fs-90r problem

Discussion in 'Mechanic and Repair' started by rockerchris, Aug 8, 2010.

  1. rockerchris

    rockerchris LawnSite Member
    Messages: 23

    Just got a brand new FS-90R trimmer a few weeks ago. All has been great until today. It took me forever to get started (at least 15-20 pulls) and once started was very difficult to keep going. The engine kept dying while idiling. I Checked the spark plug, muffler, and air filter and could not find any problems. Tomorrow I will start a fresh oil/gas mixture.

    What do you guys think? I could take the trimmer to the dealer, but I need to work tomorrow and cannot wait till the dealer can fix it. Any help is appreciated.

  2. TurboMazda

    TurboMazda LawnSite Member
    Messages: 67

    That is why the guys here at the site suggest to have 2 of each, 1 for back up in case of situations like the one you have now, did you tried adjusting the needles?
  3. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Messages: 2,248

    How many hours on unit? If I remember correctly, the FS90 is a four stroker and Stihl recommends checking the valve clearances on a somewhat regular basis but I don't know the number of hours. Being only a few weeks old, I'd suggest getting it to your dealer instead of doing something yourself that may give them reason to reject warranty.
  4. rockerchris

    rockerchris LawnSite Member
    Messages: 23

    I do not quite understand what you mean by needles? Are you talking about the Idling adjustment screw?
  5. rockerchris

    rockerchris LawnSite Member
    Messages: 23

    I would say that I have only put about 10 hours on it so far. So I do not see why it would need a valve adjustment. I think the manual suggests to check them at 153 hours. Thanks for the heads up about the warranty!
  6. unkownfl

    unkownfl LawnSite Gold Member
    Messages: 3,837

    You're SOL 99% of the time the dealer isn't going to fix it under warranty they're going to blame the duel every time... In this case I'd suggest drain the fuel and replacing it with new and add some sea foam. If that doesn't help it could need to be clean out maybe some debris got in there. The lash shoudn't be an issue at this point and time. How are you trying to start it? Try just grabbing it off the trailer and starting it without doing anything no choke no prime and see how it does.
  7. genesis215

    genesis215 LawnSite Senior Member
    Messages: 795

    Glad I saw your post, because I was using an FS 90 that behaved EXACTLY the same way. 15 pulls to start, and wouldn't idle very well, and often cut out.

    I think we need to know the answers to a couple of questions. First, does it sit on a trimmer rack on it's side or upside down? If that's the case, then you probably need a new fuel tank vent. It will also cause flooding being on it's side, which makes it hard to start. The tank vents are known to have problems from sitting on a rack in a position other than upright. The solution is to ALWAYS keep the trimmer upright. Then you won't have so much trouble. I would guess this is your main problem.

    Also, do you ever prime it when trying to start it? Priming it will cause it to be very hard to start. Just choke it, and no priming at all, and it should take right off after 1 or 2 pulls. If it doesn't start after 3 tries with the choke on, turn it off and pull without the choke. Also, only choke it for the first start of the day, and just pull and go after that. It should start right up with no choke after that first start of the day.

    Let me know what you discover. I would very much emphasize keeping it upright, and only choking it with no prime.
  8. ricky86

    ricky86 LawnSite Silver Member
    Messages: 2,096

    The primer does not flood an engine. It purges the system of air.
    My advice would to bring it back before doing anything. It might just need a simple adjustment.
  9. rockerchris

    rockerchris LawnSite Member
    Messages: 23

    Thanks for the detailed reply! It seems to be idling alright now. I took out the spark plug and cleaned as per the instructions in the manual. Really seems to have helped. I think most of my problem was flooding the engine (can you do that in a 4-mix hybrid?, I am guessing yes).

    Although it now idling, it does seem to have a noticeable increase in vibration while at idle. Was this part of the symptoms for you aswell? I think I will take it to the dealer and still get it checked out. I do not want to destroy my 2-week old $400.00 machine.
  10. genesis215

    genesis215 LawnSite Senior Member
    Messages: 795

    Yes, I would definitely recommend taking it in to the dealer take have them look at it since it's under warranty. You can flood any engine if you over choke it, and these 4-mix's don't need much choke to start. Glad you got your problem solved to an extent, if it was my trimmer I would just replace the plug.

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