Stihl FS 86 trimmer/weed whacker - good machine?

redoctobyrNovember 29, 2011


I'm considering buying a straight-shaft Stihl FS 86 trimmer. Can anyone tell me if these are good machines? Not sure if they were robust, or maybe wouldn't be a good choice. I'm going to just be giving it homeowner use, but I'd prefer something that's going to hold up well (and I'd like to go to a straight shaft, from my current curved trimmer). I don't want to simply buy a semi-disposable big-box store machine.

Anything I should check for, to see if it's in good shape? Not sure if there's a compression range to look for (eg- not less than 100 psi), or whether to look for play in the head, something like that. Thank you.

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I have an FS model something or other and it has been a good trimmer. I'm not totally in love with it w/ a brush blade- for that I prefer the 2 cycle. Trimming is great. For an inspection, just starting and running it up will tell a lot. Look for excessive vibration as the head spins, things like fuel hoses that may be starting to deteriorate etc. Pop the air filter and look that it has been doing its job and hasn't been neglected. My dealer suggested the use of the synthetic oil. You may want to ask what the original owner used. There is a service point on servicing the valve lash to consider. Mine had a fuel cap recall so if you do pick it up, give the dealer a visit and have him check it out

    Bookmark   November 29, 2011 at 1:25PM
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Good points, thanks. I should have mentioned that- this is an older one (I did not see a year mentioned in the online manual, but it makes a reference to West Germany), and is a 2-cycle. But the air filter, vibration, etc, all definitely applies.

    Bookmark   November 29, 2011 at 2:06PM
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Have had same model for 20 years. Never been in shop. Great machine for heavy work, not so great for general "household" chores.

    Bookmark   November 29, 2011 at 5:40PM
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That's great feedback, thank you. Can I ask why it's not great for lighter-duty work? Too heavy, unwieldy, something like that?

    Bookmark   November 29, 2011 at 7:02PM
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Aren't all FS models four strokes? You still use 2 cycle oil w/ the fuel- but they have an exhaust and intake valve unlike a 2 cycle. Some 4 cycle trimmers have sumps, these don't.

    Bookmark   November 30, 2011 at 6:24PM
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This one was probably ~20 years old. It was definitely a 2-stroke, per the manual.

This one's engine was in good shape, 150 psi compression. But there were unfortunately some other issues with the rest of the unit, so I decided to pass. Thank you all for the good info, I appreciate it.

    Bookmark   November 30, 2011 at 9:28PM
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fredbarber(z4 CO & z6 MA)

I have an FS85 that I bought used on eBay 8 years ago and love it. I use it on a large lot in Colorado with a bump-feed string head for wild grass encroaching on the driveway (I don't mow) and a brush blade to deal with big, tough weeds. It's perfect for the job (though mowing the weeds at the right time of year would be even more effective.)

Would it make sense to make the seller a low-ball offer and fix the other issues? If the motor's strong and easy to start, that's half the problem solved right there.

    Bookmark   December 1, 2011 at 10:24AM
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The one issue that really concerned me was that the trimmer head was bound/seized up and couldn't be turned by hand. He said it hadn't been used since the spring. I don't know whether it was stored indoors or outdoors. But the head wouldn't turn initially.

After giving it a good twist by hand a few times, we got it to loosen up and turn freely. After that, it would spin when the engine sped up. When you'd start it, the engine would be turning "slowly" (clutch would not engage). But over the next 10 seconds or whatever, it would gradually speed up (with the choke off), and the head would start to turn. I could feel vibration in the shaft when the head was spinning, with no line coming out of the head (so not just an imbalance due to string issues). When you'd kill the engine, with the head spinning, I'd hear a noise from the engine/clutch area as the head slowed down, which sounded like maybe a worn/noisy bearing. Not in the engine, but on the output shaft side, after the clutch (the noise slowed down at the same rate as the trimmer head).

I don't know what was bound up initially, whether down by the trimmer head, or closer to the engine. I don't know whether that vibration, and bearing (?) noise is normal, but they kind of scared me off. Carb tuning, etc, I have no problem with. But I was leery of getting into something where perhaps bearings might seize up on me, in the shaft? Or, again, maybe the vibration & shaft noise are normal.

    Bookmark   December 1, 2011 at 11:26AM
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fredbarber(z4 CO & z6 MA)

Some noise and vibration is normal, but it's difficult to say from your description whether this one falls within the normal range or not. I haven't had the shaft off mine, so I don't have first hand knowledge of its construction or possible wear points.

If you're handy and don't mind taking a little bit of a risk, you could research the salvage value of a good motor with a bad shaft on eBay (or just the powerhead alone; might not be exactly the same model, but a range) and make the guy an offer in that area. Get a shop manual (which you should do anyway). Make sure the gear head is properly packed with the right grease (also a must). Then play it by ear. Monitor eBay for whatever you think you might have to replace at a good price. (With the off-season approaching, it's bargain hunting time!) You might end up with a great trimmer at a low price, and even if the shaft craps out you might be able to recover enough from the sale of the motor to make the cost of ownership pretty low.

    Bookmark   December 2, 2011 at 8:05AM
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