Author Topic: Stihl HS86T Hedge Trimmer--High compression?  (Read 550 times)

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Offline Giles

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Stihl HS86T Hedge Trimmer--High compression?
« on: July 03, 2013, 01:28:16 pm »
No--it's not a chainsaw but engine is close????
I recently bought a Stihl HS86T Hedge Trimmer. It was understood that it had a running issue, mainly wouldn't idle. After a thorough cleaning, I found the muffler spark arrestor completely plugged :o
The trimmer runs perfect and idles fine but the problem is with pull start :(
This was bought for my wife and she has no trouble cranking her Echo string trimmer, leaf blower or even my chainsaws.
However this trimmer has so much compression, she has trouble with going through ONE compression stroke >:(
I am not new to two stroke engines and have rebuilt hundreds.
Now, since the screen was so blocked, I am suspecting a high amount of carbon build up in the combustion chamber. Just hate to teardown a perfectly running engine.
Have any of you ran into this before?

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Offline 660magnum

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Re: Stihl HS86T Hedge Trimmer--High compression?
« Reply #1 on: July 03, 2013, 02:05:16 pm »
I have a Stihl HS-80 hedge trimmer and the compression doesn't seem unusual.
I also have Stihl HS-45, HS-55 string trimmers, and a 025 chainsaw that have what feels like high compression and it would take a mean - determined woman to start one of them.
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Offline Giles

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Re: Stihl HS86T Hedge Trimmer--High compression?
« Reply #2 on: July 03, 2013, 02:23:26 pm »
Well, she's definitely mean but not very strong or determined  :)
Another strange thing is that I can't find a single on-line parts diagram for this hedger, even from stihl >:(
This is a commercial product that is About three years old and I have only found the operators manual ???
I just feel that there would have to be an enormous amount of carbon to cause this problem.
I will have to find a way to use my compression tester because it has the tiny sparkplug.
That will be simpler then tearing into
the engine.

Offline Fish

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Re: Stihl HS86T Hedge Trimmer--High compression?
« Reply #3 on: July 03, 2013, 03:38:13 pm »
Actually, it takes very little carbon buildup to become a problem.  But the problem could be from a floody carb as well, so you might look in the carb as well,
as it might be a leaky needle or welch plug.
    To isolate the trouble, you could drain and totally dry out the engine/fuel system, totally, and if you still have a high compression problem, then carbon buildup would be the likely culprit.  I am going to start a mediacat thread here, so you can get the parts blowup and the mechanics manual.


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