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Stihl fs111rs vibration?

Discussion in 'Lawn Mowing Equipment' started by lasher66, Sep 25, 2017.

  1. lasher66

    lasher66 LawnSite Senior Member
    Messages: 399

    Hello,
    For the last 10 yrs we always used the fs100rs trimmers and stihl decided to change the design and call it the 111rs now I guess. Anyways I bought one last month and my employees and I all notice it vibrates slightly enough to get very annoying after a big job. Just wondering if anyone else noticed this problem. I can hold the 100 in one hand and 111 in the other and pull the trigger and notice a big difference in how smooth they are. I already took it back and they replaced the shaft and transmission they said. I already replaced the head also. Still does the same thing. Would like to know if its just this unit or the new design. Thanks

    Jason
     
  2. Merkava_4

    Merkava_4 LawnSite Bronze Member
    Messages: 1,441

    It might be the flywheel out of balance; that's about the only thing left if they already replaced the drive tube assembly and the gearbox.
     
  3. Ridin' Green

    Ridin' Green LawnSite Fanatic
    Male, from Michigan
    Messages: 17,649

    Are you running the stock heads or the speed feeds?
     
  4. Reliable 1

    Reliable 1 LawnSite Member
    Messages: 188

    I purchased a FS 111R and noticed the exact same thing. I changed out my cutter head to Speed Feed. Still had the same issue. I also had removed my guard. Not satisfied, I took mine to the dealer, they tested it and observed the same thing. The tech told me it was because Stihl designed the new trimmers to be operated with the guards on...and without the guards, longer trimmer lines beyond a normal length (guard on) creates an imbalance. Long story short, the excessive vibration was reduced with the guard on, but I am not totally convinced that their isn't an issue with the new unit.
     
    Ridin' Green likes this.
  5. Merkava_4

    Merkava_4 LawnSite Bronze Member
    Messages: 1,441

    I just thought of something - does the FS 111 R have a hollow driveshaft ? If so, those things are hard to balance. Echo tried to go with a hollow driveshaft on their new SRM-2620, but had to switch to a cable drive because of vibration issues.
     
  6. Blainethompson

    Blainethompson LawnSite Senior Member
    Messages: 355

    only the rx models have the hollow aluminum drive shaft. I was under the understanding that the only changes made to the 90-91 130-131 etc etc. was the motor. new choke set up, the little computer they added for collecting engine and run data, and an easy access hole to get to the valve cover. id have to go back and read up but I don't think they changed anything besides things on the actual motor I just mentioned. does the vibration increase with rpms? if you rev up the motor and then quickly let off letting the cutting head continue to spin and the motor rpms going down does the vibration follow the motor or cutting head rpms (that explanation makes sense in my head) get what I'm saying?
     
  7. Reliable 1

    Reliable 1 LawnSite Member
    Messages: 188

    I can't speak for the OP, but on mine, it definitely increases as the RPM's increase. I have a variety of Stihl trimmers...I'm gonna play around with the different shafts to see if it makes a difference.
     
  8. Blainethompson

    Blainethompson LawnSite Senior Member
    Messages: 355

    It defiantly sounds to me like its coming from the drive shaft. the drive shaft being replaced and the vibration still being there kinda throws a curveball on my idea though. Something I would have to put my hands on to figure out.
     
  9. Reliable 1

    Reliable 1 LawnSite Member
    Messages: 188

    Just tested the shaft theory...the FS 111R has a solid shaft, and my FS 94R has a hollow shaft. Same dimensions. I swapped them, and definitely notice a big difference in the amount of vibration. As for my concerns regarding torque on hollow shaft vs. solid shaft, none...as I have FS 130's and a FS 250 for the attachments.
     
  10. Blainethompson

    Blainethompson LawnSite Senior Member
    Messages: 355

    Solid aluminum shaft or steel?
     

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