Stihl FS90R carb repair - replace gasket/diaphragms (pictorial)

Discussion in 'Mechanic and Repair' started by Roger, Sep 26, 2010.

  1. Richard Martin

    Richard Martin LawnSite Fanatic
    Messages: 14,699

    I agree with others that it should have been cleaned prior to disassembly. Also at 4 years I would have replaced all of the fuel lines, the primer bulb and the fuel filter. I hate to say it but you really only did a half assed job on this carb rebuild. All needles and jets should have been removed and all of the orifices cleaned out. You're setting yourself up for more fuel issues in the not too distant future by taking these shortcuts. Sorry but that's the way I see it. Your opinion may differ from mine.
  2. Roger

    Roger LawnSite Fanatic
    Messages: 5,943

    Richard, thanks for the suggestions.

    In my experience, one carb repair is about par for the life of machines like this. This repair was done part way through its life, and I did not need to be concerned about "more fuel issues ... not too distant future..." It lasted long enough for another major problem, so having a good carb on the machine with a failed drive line isn't of much value. I have never replaced needles and jets on any carb rebuild, and never been worse for it in the future. Apparently, these parts have a much greater lifespan than the diaphragms.

    This trimmer now sits in the shop, and I'm wondering if it should be repaired. The square shank on the drive line has worn out, and will no longer engage with the clutch plate. It is on my list to disassemble to see how many parts are required to put it back into service. It has been replaced.

    I've not seen anybody post anything about making this kind of repair. Or, maybe they made the repair, but posted no pics so others might understand what is involved.
  3. Richard Martin

    Richard Martin LawnSite Fanatic
    Messages: 14,699

    If you're talking about the driveshaft, it carries a lifetime warranty from Stihl.
  4. bls47303

    bls47303 LawnSite Senior Member
    from Indiana
    Messages: 354

    Ive found in the past that the carb rebuild kits are about $10 to $12 less than just buying a new carb for the FS90R trimmers and in the time it saves to just swap it out when your in the middle of the busy seson its worth it.
  5. cpllawncare

    cpllawncare LawnSite Silver Member
    Messages: 2,659

    I was told the same thing by a small engine mechanic, just replace the whole carb don't bother with a rebuild.
  6. norcoprop

    norcoprop LawnSite Member
    Messages: 7

    I own all Stihl handhelds, Fs130, Fs90, (2)Br550's and a br600 all have had carbs replaced @ $75 for the carb and a minimum of $50 for labor, the rebuild kit at $10 dollars sounds like a wise choice. These carbs only seem to be lasting 3-4 months,so a rebuild would save me a fair amount in the life span of my handhelds. Thanks for the tutorial at this time the Fs90 and Br600 are less than a year old and both are needing carb help now, Fs130 is 3 years old and has had 5 carbs and is ready again(Thank you Ethanol)
  7. Will P.C.

    Will P.C. LawnSite Senior Member
    Messages: 966

    I have been told by 2 master mechanics with a combined 50+ years in the small engine biz) to just replace the carb instead of worrying about kits, and rebuilding/cleaning the carbs. It is labor intensive and can be difficult cleaning out all those little holes on a carb.

    I paid about 35 shipped for a brand new carb off ebay for a Stihl Blower

    On another note, you should be getting more than 3-4 months out of commercial hand helds. Something isn't adding up
  8. norcoprop

    norcoprop LawnSite Member
    Messages: 7

    That's my thoughts and according to the dealer Stihl is not warrantying the carbs anymore because they cant be sure what people are running in them.Always 89 octane and the Stihl ultra mix oil.I use 5 gals every 8 days so the gas is not stale. I bring them to the dealer and get them back with a new carb at $125 a whack. the Br600 is going through a spell right now with these warm days sitting in the back of the truck heat expansion is forcing gas out the carb saturating the air filter and wont start unless I pull the air filter off.brought that in and asked them to check the vent. they said that was fine probably gonna need a new carb. I bought this in November last year so it saw Nov,May,June,and part of July before needing new carb. Fs90 was Purchased Oct last year and is in the same schedule for carb replacement
  9. Richard Martin

    Richard Martin LawnSite Fanatic
    Messages: 14,699

    Find another dealer. Stihl warrants every part of every gas powered tool. Period. If they were that concerned about your fuel they would take a sample and test it. The percentage of Ethanol in gas is easily tested with a dirt cheap tool. The dealer can do it. You can do it.
  10. dboyd351

    dboyd351 LawnSite Bronze Member
    Messages: 1,126

    Bet he did at $125 a pop!

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